U.S. patent application number 17/163691 was filed with the patent office on 2021-07-29 for antenna device.
This patent application is currently assigned to Yokowo Co., Ltd.. The applicant listed for this patent is Yokowo Co., Ltd.. Invention is credited to Takeshi SAMPO, Takayuki SONE.
Application Number | 20210234284 17/163691 |
Document ID | / |
Family ID | 1000005554627 |
Filed Date | 2021-07-29 |
United States Patent
Application |
20210234284 |
Kind Code |
A1 |
SAMPO; Takeshi ; et
al. |
July 29, 2021 |
ANTENNA DEVICE
Abstract
An antenna device includes: a pair of first elements that are
arranged on a first plane; and a pair of second elements that are
arranged on a second plane parallel to the first plane such that a
polarized wave direction of the pair of second elements is
orthogonal to that of the pair of first elements. Each element of
the pair of first elements and the pair of second elements includes
a portion that acts as a self-similarity antenna or an antenna that
acts based on similar operating principle to the self-similarity
antenna. in one embodiment, each element of the pair of first
elements and the pair of second elements includes two arms that
extend in a direction away from each other from a proximal end
portion to which a feed point is connectable.
Inventors: |
SAMPO; Takeshi;
(Tomioka-Shi, JP) ; SONE; Takayuki; (Tomioka-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Yokowo Co., Ltd. |
Tokyo |
|
JP |
|
|
Assignee: |
Yokowo Co., Ltd.
Tokyo
JP
|
Family ID: |
1000005554627 |
Appl. No.: |
17/163691 |
Filed: |
February 1, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2019/029899 |
Jul 30, 2019 |
|
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17163691 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01Q 21/24 20130101;
H01Q 9/16 20130101 |
International
Class: |
H01Q 21/24 20060101
H01Q021/24; H01Q 9/16 20060101 H01Q009/16 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 2018 |
JP |
2018-143828 |
Claims
1. An antenna device, comprising: a pair of first elements that are
arranged on a first plane; and a pair of second elements that are
arranged on a second plane parallel to the first plane such that a
polarized wave direction of the pair of second elements is
orthogonal to that of the pair of first elements, wherein each
element of the pair of first elements and the pair of second
elements includes a portion that acts as a self-similarity antenna
or an antenna that acts based on similar operating principle to the
self-similarity antenna.
2. The antenna device according to claim 1, wherein: each element
of the pair of first elements and the pair of second elements
includes two arms that extend in a direction away from each other
from a proximal end portion to which a feed point is connectable;
and the two arms act as a self-similarity antenna or an antenna
that acts based on similar operating principle to the
self-similarity antenna.
3. The antenna device according to claim 2, wherein, in a case
where a first center portion and a second center portion overlap
each other when viewed from a plane, the first center portion being
a midpoint of a distance between the proximal end portion of one
first element of the pair of first elements and the proximal end
portion of the other first element, and the second center portion
being a midpoint of a distance between the proximal end portion of
one second element of the pair of second elements and the proximal
end portion of the other second element, the pair of second
elements are arranged to face the pair of first elements in a state
in which the pair of second elements are turned by approximately 90
degrees from a position at which the second center portion is
aligned with the first center position.
4. The antenna device according to claim 3, wherein a teed point is
connected to at least one of the first center portion and the
second center portion.
5. The antenna device according to claim 2, wherein a facing
distance between the two arms is increased as being away from a
vicinity of the proximal end portion.
6. The antenna device according to claim 2, wherein a width of each
of the two arms is increased as being away from the proximal end
portion.
7. The antenna device according to claim 2, wherein two arms
included in one first element of the pair of first elements and two
arms included in the other first element of the pair of first
elements extend in a direction away from each other.
8. The antenna device according to claim 2, wherein the two arms
have open end portions at respective distal ends to form, together
with the proximal end portion, any one of a substantially C shape,
a substantially D shape, a substantially U shape, a substantially V
shape, a substantially semicircular shape, a substantially
semiellipse shape, a substantially triangular shape, and a
substantially quadrangular shape.
9. The antenna device according to claim 8, wherein a portion of
the open end portion is bent in a direction toward the other facing
element.
10. The antenna device according to claim 2, wherein the two arms
in the pair of first elements are conductively connected to or
capacitively coupled to the closest arm in the two arms of the pair
of second elements, whereby the pair of first elements and the pair
of second elements act as a loop antenna, a dipole antenna, a
tapered-slot antenna, or a complex antenna in which such antennas
are combined, according to an available frequency band.
11. An antenna device, comprising: a pair of first elements that
are arranged on a first plane; and a pair of second elements that
are arranged on a second plane parallel to the first plane, so that
a polarized wave direction of the pair of second elements is
orthogonal to that of the pair of first elements, wherein each
element of the pair of first elements and the pair of second
elements includes a proximal end portion to which a feed point is
connected, and a pair of arms that are arranged on one plane
symmetrically about the proximal end portion, and at least one arm
of the pair of arms acts as a self-similarity antenna or an antenna
that acts based on similar operating principle to the
self-similarity antenna.
12. The antenna device according to claim 1, wherein, in a
frequency band from 698 MHz and frequencies before and after 698
MHz to 6 GHz and frequencies before and after 6 GHz, a signal in a
specific frequency band is receivable or transmittable.
13. An antenna device, comprising: a first element and a second
element that are arranged on one plane; and a feed point that
enables feeding to the first element and the second element,
wherein each of the first element and the second element includes
two arms and a proximal end portion to which the feed point is
connected, the first element and the second element face each other
across the feed point, and each includes a portion that acts as a
self-similarity antenna or an antenna that acts based on similar
operating principle to the self-similarity antenna, the two arms of
the first element extend in a direction away from each other from
the proximal end portion, the two arms of the second element extend
in a direction away from each other from the proximal end portion,
and each extends in a direction away from facing one of the two
arms of the first element, and a facing distance between the first
element and the second element is continuously or gradually
increased as being away from the proximal end portion.
14. The antenna device according to claim 13, wherein, in the two
arms of the first element and the two arms of the second element,
each width is larger in a portion far from the proximal end portion
than in a portion close to the proximal end portion.
15. The antenna device according to claim 13, wherein the two arms
have open end portions at respective distal ends to form, together
with the proximal end portion, any one of a substantially C shape,
a substantially D shape, a substantially U shape, a substantially V
shape, a substantially semicircular shape, a substantially
semiellipse shape, a substantially triangular shape, and a
substantially quadrangular shape.
16. The antenna device according to claim 13, wherein the first
element and the second element are symmetrical about the feed
point.
17. The antenna device according to claim 1, a first region
including a portion to which a feed point is connected is formed on
a board, the portion being a portion of an element in at least one
of the pair of first elements and the pair of second elements, a
second region other than the first region is formed by a metal
plate, and the first region and the second region are conductively
connected to each other.
18. The antenna device according to claim 1, wherein the pair of
first elements and the pair of second elements are formed on a
board.
19. The antenna device according to claim 13, a first region
including a portion to which a feed point is connected is formed on
a board, the portion being a portion of at least one element of the
first element and the second element; a second region other than
the first region is formed by a metal plate and the first region
and the second region are conductively connected to each other,
20. The antenna device according to claim 13, wherein the first
elements and the pair of second elements are formed on a board.
21. The antenna device according to claim 1, wherein the first
element and the second element facing the first element act as
antennas having different operating principles or a complex antenna
in which the different operating principles are combined, according
to a frequency band.
22. The antenna device according to claim 21, wherein the pair of
first elements and the pair of second elements facing the pair of
first elements are capacitively coupled, whereby the pair of first
elements and the pair of second elements act as antennas having
different operating principles or a complex antenna in which the
different operating principles are combined, according to a
frequency band.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of International
Application No. PCT/JP2019/029899, filed on Jul. 30, 2019, which
claims priority to Japanese Patent Application No. 2018-143828,
filed on Jul. 31, 2018, the entire disclosure of each are
incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to a thin profile antenna
device that is usable in a wide frequency range from 698 MHz and
frequencies before and after 698 MHz to 6 GHz and frequencies
before and after 6 GHz, for example.
BACKGROUND ART
[0003] In recent years, there has been increasing demand for
conducting multiple-input multiple-output (MIMO) communication
using a frequency band of long term evolution (LTE) or the fifth
generation mobile communication system (5G) for vehicles carrying
electronic equipment. The MIMO is a communication mode that uses
plural antennas to transmit different data from each antenna and
receive data simultaneously by the plural antennas. A MIMO antenna
device disclosed in Patent Literature 1 is known as an antenna
device enabling such a communication mode.
[0004] The MIMO antenna device disclosed in Patent Literature 1
includes plural antennas, that is, a balanced antenna and an
unbalanced antenna that are accommodated in a shark fin antenna
housing having 100 mm long, 50 mm wide, and 45 mm high. The
unbalanced antenna is constituted. by a rectangular planar etching
formed of polychlorinated biphenyl. The balanced antenna includes
two symmetrical planar L-shaped arms that face each other.
PRIOR ART DOCUMENTS
Patent Literature
[0005] Patent Literature 1: National Publication of International
Patent Application No. 2016-504799
SUMMARY OF INVENTION
Problems to Be Solved by the Invention
[0006] When the unbalanced antenna is made low profile as with the
MIMO antenna device disclosed in Patent Literature 1, the antenna
size (height) decreases, resulting in deterioration of a voltage
standing wave ratio (VSWR) and shortage of gain in the horizontal
direction. When plural antennas are accommodated in a small area
such as the shark fin antenna housing, interference occurs between
the antennas, which adversely affects the antenna characteristic.
For example, in the MIMO antenna device used in LTE, greater
isolation between the antennas is preferable, but in the MIMO
antenna device disclosed in Patent Literature 1, it is difficult to
satisfy such a condition over a wide frequency band. As illustrated
in FIGS. 5 to 7 of Patent Literature 1, available frequency bands
are limited to plural points in a frequency range from 0.6 to 3
GI4z, and the respective frequency bands are narrow.
[0007] The present invention has a primary object to enable a
stable operation over a wide frequency band and further has an
object to provide an antenna device capable of reducing the effect
of another adjacent antenna or element.
Solution to the Problems
[0008] An antenna device according to one embodiment of the present
invention includes a pair of first elements that are arranged on a
first plane, and a pair of second elements that are arranged on a
second plane parallel to the first plane, so that a polarized wave
direction of the pair of second elements is orthogonal to that of
the pair of first elements, wherein each element of the pair of
first elements and the pair of second elements includes a portion
that acts as a self-similarity antenna or that acts based on
similar operating principle to the self-similarity antenna.
[0009] More specifically, each element of the pair of first
elements and the pair of second elements includes two arms that
extend in a direction away from each other from a proximal end
portion to which a feed point is connectable, and the two arms act
as a self-similarity antenna or an antenna that acts based on
similar operating principle to the self-similarity antenna. The
"self-similarity antenna" is an antenna including, for example, a
biconical antenna or a bow-tie antenna, in which a shape thereof is
similar even when a scale (size ratio) is changed.
Advantageous Effects of the Invention
[0010] Since the antenna device of the present invention includes
the pair of first elements and the pair of second elements in which
a polarized wave direction of the pair of second elements is
orthogonal to that of the pair of first elements, and each of the
pair of first elements and the pair of second elements includes a
portion that acts as a self-similarity antenna or an antenna that
acts based on similar operating principle to the self-similarity
antenna, the antenna device acts as, for example, a tapered-slot
antenna (one type of traveling-wave-type antennas) in a high
frequency side which is a relatively high frequency band, and acts,
for example, a loop antenna (one type of resonant antennas) in a
low frequency side which is a relatively low frequency band. The
antenna device acts as a dipole antenna (one type of resonant
antennas) in a specified frequency band in a middle frequency range
which is a mid-frequency band between the relatively high frequency
band and the relatively low frequency band. In frequency bands
among the relatively high frequency band, the relatively low
frequency band, and the middle frequency region, the antenna device
operates in a state in which operating principles of the antennas
are combined, that is, acts as a complex antenna. Therefore, using
one antenna device, a stable operation can be achieved over a wider
frequency band than this type of conventional antenna device.
[0011] Since the polarized wave direction of the first elements is
orthogonal to that of the second elements, the influence such as
interference can be reduced even when the first elements and the
second elements are brought close to each other. Therefore, a
thin-profile antenna device can be provided.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1A is a perspective view of a case body in which an
antenna unit of a first embodiment is to be accommodated.
[0013] FIG. 1B is a cross-sectional view of one side portion of
FIG. 1A.
[0014] FIG. 2A is a front view of the antenna unit of the first
embodiment.
[0015] FIG. 2B is a rear view of the antenna unit of the first
embodiment.
[0016] FIG. 2C is a top view of the antenna unit of the first
embodiment.
[0017] FIG. 2D is a perspective view of the antenna unit of the
first embodiment.
[0018] FIG. 3A is an illustrative diagram of one and the other of
second elements.
[0019] FIG. 3B is an illustrative diagram of a pair of second
elements.
[0020] FIG. 4A is a graph showing a VSWR characteristic of one
element.
[0021] FIG. 4B is a graph showing a radiation efficiency
characteristic of one element.
[0022] FIG. 4C is a graph showing an average gain characteristic in
a horizontal plane of the antenna of FIG. 3A.
[0023] FIG. 5A is a graph showing a VSWR characteristic of two
elements.
[0024] FIG. 5B is a graph showing a radiation efficiency
characteristic of two elements.
[0025] FIG. 5C is a graph showing an average gain characteristic in
a horizontal plane of the antenna of FIG. 3B.
[0026] FIG. 6A is a graph showing a VSWR characteristic of a feed
point K1 in the first embodiment.
[0027] FIG. 6B is a graph showing a VSWR. characteristic of a feed
point K2 in the first embodiment.
[0028] 7A is a graph showing a radiation efficiency characteristic
of the feed point K1 in the first embodiment.
[0029] FIG. 7B is a graph showing a radiation efficiency
characteristic of the feed point K2 in the first embodiment.
[0030] FIG. 8A is a graph showing a passing power characteristic
from the feed point K1 to the feed point K2 in the first
embodiment.
[0031] FIG. 8B is a graph showing a passing power characteristic
from the feed point K2 to the feed point K1 in the first
embodiment.
[0032] FIG. 9A is a front view of the antenna unit of the first
embodiment.
[0033] FIG. 9B is a front view illustrating a state in which the
antenna unit of the first embodiment is inclined by a predetermined
angle.
[0034] FIG. 10A is a graph showing an average gain characteristic
in the horizontal plane of the feed point K1 in an arrangement of
FIG. 9A,
[0035] FIG. 10B is a graph showing an average gain characteristic
in the horizontal plane of the feed point K2 in the arrangement of
FIG. 9A.
[0036] FIG. 11A is a graph showing an average gain characteristic
in the horizontal plane of the feed point K1 in an arrangement of
FIG. 9B.
[0037] FIG. 11B is a graph showing an average gain characteristic
in the horizontal plane of the feed point K2 in the arrangement of
FIG. 9B.
[0038] FIG. 12A is a front view of an antenna unit of the
comparative example.
[0039] FIG. 12B is a rear view of the antenna unit of the
comparative example.
[0040] FIG. 12C is a top view of the antenna unit of the
comparative example.
[0041] FIG. 12D is a perspective view of the antenna unit of the
comparative example.
[0042] FIG. 13A is a graph showing a VSWR characteristic of the
antenna unit of the comparative example.
[0043] FIG. 13B is an enlarged graph showing a low frequency
portion of FIG. 13A.
[0044] FIG. 14A is a graph showing a radiation efficiency
characteristic of the antenna unit of the comparative example.
[0045] FIG. 14B is an enlarged graph showing a low frequency
portion of FIG. 14A.
[0046] FIG. 15A is a front view of an antenna unit of a second
embodiment.
[0047] FIG. 15B is a rear view of the antenna unit of the second
embodiment.
[0048] FIG. 15C is a top view of the antenna unit of the second
embodiment.
[0049] FIG. 15D is a perspective view of the antenna unit of the
second embodiment.
[0050] FIG. 16A is a graph showing a VSWR characteristic of a feed
point K1 in the second embodiment.
[0051] FIG. 16B is a graph showing a VSWR characteristic of a feed
point K2 in the second embodiment.
[0052] FIG. 17A is a graph showing a radiation efficiency
characteristic of the feed point K1 in the second embodiment.
[0053] FIG. 17B is a graph showing a radiation efficiency
characteristic of the feed point K2 in the second embodiment.
[0054] FIG. 18A is a graph showing a passing power characteristic
from the feed point K1 to the teed point K2 in the second
embodiment.
[0055] FIG. 18B is a graph showing a passing power characteristic
from the feed point K2 to the feed point K1 in the second
embodiment.
[0056] FIG. 19A is a graph showing an average gain characteristic
in a horizontal plane of the feed point K1 in the arrangement of
FIG. 15A.
[0057] FIG. 19B is a graph showing an average gain characteristic
in the horizontal plane of the feed point K2 in the arrangement of
FIG. 15A.
[0058] FIG. 20A is a front view of an antenna unit of a third
embodiment.
[0059] FIG. 20B is a top view of a long side portion of the antenna
unit of the third embodiment.
[0060] FIG. 20C is a side view of a short side portion of the
antenna unit of the third embodiment.
[0061] FIG. 20D is a perspective view of the antenna unit of the
third embodiment.
[0062] FIG. 21A is a graph showing a VSWR characteristic of a feed
point K1 in the third embodiment.
[0063] FIG. 21B is a graph showing a VSWR characteristic of a feed
point K2 in the third embodiment.
[0064] FIG. 22A is a graph showing a radiation efficiency
characteristic of the feed point K1 in the third embodiment.
[0065] FIG. 22B is a graph showing a radiation efficiency
characteristic of the feed point K2 in the third embodiment,
[0066] FIG. 23A is a graph showing a passing power characteristic
from the feed point K1 to the feed point K2 in the third
embodiment
[0067] FIG. 23B is a graph showing a passing power characteristic
from the feed point K2 to the feed point K1 in the third
embodiment.
[0068] FIG. 24A is a graph showing an average gain characteristic
in a. horizontal plane of the feed point K1 in the arrangement of
FIG. 20A.
[0069] FIG. 24B is a graph showing an average gain characteristic
in the horizontal plane of the feed point K2 in the arrangement of
FIG. 20A.
[0070] FIG. 25A is a front view of an antenna unit of a fourth
embodiment,
[0071] FIG. 25B is a top view of the antenna unit of the fourth
embodiment.
[0072] FIG. 25C is a perspective view of the antenna unit of the
fourth embodiment.
[0073] FIG. 26A is a graph showing a VSWR characteristic of a feed
point K1 in the fourth embodiment.
[0074] FIG. 26B is a graph showing a VSWR characteristic of a teed
point K2 in the fourth embodiment.
[0075] FIG. 27A is a graph showing a radiation efficiency
characteristic of the feed point K1 in the fourth embodiment.
[0076] FIG. 27B is a graph showing a radiation efficiency
characteristic of the feed point K2 in the fourth embodiment.
[0077] FIG. 28A is a graph showing a passing power characteristic
from the feed point K1 to the teed point K2 in the fourth
embodiment.
[0078] FIG. 28B is a graph showing a passing power characteristic
from the feed point K2 to the feed point K1 in the fourth
embodiment.
[0079] FIG. 29A is a graph showing an average gain characteristic
in a horizontal plane of the feed point K1 in the arrangement of
FIG. 24A.
[0080] FIG. 29B is a graph showing an average gain characteristic
in the horizontal plane of the feed point K2 in the arrangement of
FIG. 24A.
[0081] FIG. 30A is a perspective view of a front side of the
antenna unit of the fifth embodiment.
[0082] FIG. 30B is a perspective view of a rear side of the antenna
unit of the fifth embodiment.
[0083] FIG. 31A is a perspective view of an antenna unit in a sixth
embodiment.
[0084] FIG. 31B is a front view illustrating a feeding state of
first elements in the sixth embodiment.
[0085] FIG. 31C is a front view illustrating a feeding state of
second elements in the sixth embodiment.
[0086] FIG. 32A is a graph showing a VSWR characteristic of an
output end of a coaxial cable F114 in the sixth embodiment.
[0087] FIG. 32B is a graph showing a VSWR characteristic of an
output end of a coaxial cable F214 in the sixth embodiment.
[0088] FIG. 32C is a graph showing a radiation efficiency
characteristic of the output end of the coaxial cable F114 in the
sixth embodiment.
[0089] FIG. 32D is a graph showing a radiation efficiency
characteristic of the output end of the coaxial cable F214 in the
sixth embodiment.
[0090] FIG. 32E is a graph showing a passing power characteristic
from the output end of the coaxial cable F114 to the output end of
the coaxial cable F214 in the sixth embodiment.
[0091] FIG. 32F is a graph showing a passing power characteristic
from the output end of the coaxial cable F214 to the output end of
the coaxial cable F114 in the sixth embodiment.
[0092] FIG. 32G is a graph showing an average gain characteristic
in a horizontal plane of the output end of the coaxial cable F114
in the arrangement of FIG. 31A.
[0093] FIG. 32H is a graph showing an average gain characteristic
in the horizontal plane of the output end of the coaxial cable F214
in the arrangement of FIG. 31A.
[0094] FIG. 33A is a front view of first elements in a seventh
embodiment.
[0095] FIG. 33B is a front view of second elements in the seventh
embodiment.
[0096] FIG. 33C is a front view illustrating a feeding state of the
first elements in the seventh embodiment.
[0097] FIG. 33D is a front view illustrating a feeding state of
second elements in the seventh embodiment.
[0098] FIG. 33E is a perspective view for illustrating the overall
state of the first elements and the second elements.
[0099] FIG. 33F is a side view of the antenna unit of the seventh
embodiment.
[0100] FIG. 34A is a graph showing a VSWR characteristic of an
output end of a coaxial cable F114 in the seventh embodiment.
[0101] FIG. 34B is a graph showing a VSWR characteristic of an
output end of a coaxial cable F214 in the seventh embodiment.
[0102] FIG. 34C is a graph showing a radiation efficiency
characteristic of the output end of the coaxial cable F 114 in the
seventh embodiment.
[0103] FIG. 34D is a graph showing a radiation efficiency
characteristic of the output end of the coaxial cable F214 in the
seventh embodiment.
[0104] FIG. 34E is a graph showing a passing power characteristic
from the output end of the coaxial cable F114 to the output end of
the coaxial cable F214 in the seventh embodiment.
[0105] FIG. 34F is a graph showing a passing power characteristic
from the output end of the coaxial cable F214 to the output end of
the coaxial cable F114 in the seventh embodiment.
[0106] FIG. 34G is a graph showing an average gain characteristic
in a. horizontal plane of the output end of the coaxial cable F114
in the arrangement of FIG. 31A.
[0107] FIG. 34H is a graph showing an average gain characteristic
in the horizontal plane of the output end of the coaxial cable F214
in the seventh embodiment.
[0108] FIG. 35A is a graph showing a VSWR characteristic of the
output end of the coaxial cable F114 according to a modification
example.
[0109] FIG. 35B is a graph showing a VSWR characteristic of the
output end of the coaxial cable F214 according to the modification
example.
[0110] FIG. 35C is a graph showing a radiation efficiency
characteristic of the output end of the coaxial cable F114
according to the modification example.
[0111] FIG. 35D is a graph showing a radiation efficiency
characteristic of the output end of the coaxial cable F214
according to the modification example.
[0112] FIG. 35E is a graph showing a passing power characteristic
from the output end of the coaxial cable F114 to the output end of
the coaxial cable F214 according to the modification example.
[0113] FIG. 35F is a graph showing a passing power characteristic
from the output end of the coaxial cable F214 to the output end of
the coaxial cable F114 according to the modification example.
[0114] FIG. 35G is a graph showing an average gain characteristic
in a horizontal plane of the output end of the coaxial cable F114
in the arrangement of FIG. 31A.
[0115] FIG. 35H is a graph showing an average gain characteristic
in the horizontal plane of the output end of the coaxial cable F214
according to the modification example.
[0116] FIG. 36A is a perspective view illustrating an example of an
overall configuration of an antenna unit of an eighth
embodiment.
[0117] FIG. 36B is a front view illustrating a feeding state of
first elements in the eighth embodiment.
[0118] FIG. 36C is a front view illustrating a feeding state of
second elements in the eighth embodiment.
[0119] FIG. 37A is a graph showing a VSWR characteristic of an
output end of a coaxial cable F114 in the eighth embodiment,
[0120] FIG. 37B is a graph showing a VSWR characteristic of an
output end of a coaxial cable F214 in the eighth embodiment.
[0121] FIG. 37C is a graph showing a radiation efficiency
characteristic of the output end of the coaxial cable F114 in the
eighth embodiment.
[0122] FIG. 37D is a graph showing a radiation efficiency
characteristic of the output end of the coaxial cable F214 in the
eighth embodiment.
[0123] FIG. 37E is a graph showing a passing power characteristic
from the output end of the coaxial cable F114 to the output end of
the coaxial cable F214 in the eighth embodiment.
[0124] FIG. 37F is a graph showing a passing power characteristic
from the output end of the coaxial cable F214 to the output end of
the coaxial cable F114 in the eighth embodiment.
[0125] FIG. 37G is a graph showing an average gain characteristic
in a horizontal plane of the output end of the coaxial cable F114
in the arrangement of FIG. 36A.
[0126] FIG. 37H is a graph showing an average gain characteristic
in the horizontal plane of the output end of the coaxial cable F214
in the arrangement of FIG. 36A.
[0127] FIG. 38 is an external view of an antenna device in a ninth
embodiment.
[0128] FIG. 39 is an exploded view of the antenna device in the
ninth embodiment.
[0129] FIG. 40A is a perspective view of an inside of a first case
body, when viewed from a rear side.
[0130] FIG. 40B is a front view of the inside of the first case
body.
[0131] FIG. 40C is a perspective view of an inside of a second case
body, when viewed from a rear side.
[0132] FIG. 40D is a front view of the inside of the second case
body.
DESCRIPTION OF EMBODIMENTS
[0133] A description will hereinafter be made with reference to the
drawings about examples of embodiments in which the present
invention is applied to an antenna device that is usable in a wide
frequency band from 698 MHz and frequencies before and after 698
MHz to 6 GHz and frequencies before and after 6 GHz.
First Embodiment
[0134] An antenna device of a first embodiment is used in a state
in which an antenna unit is accommodated in a thin profile case
that can be installed in any posture at any position inside a room
or a vehicle compartment, for example. The thin profile case
includes a case body formed of a member having electric wave
permeability, such as an ABS resin, and a holding part formed
appropriately according to an installation position. The case body
includes, for example, a bottomed rectangular parallelepiped-shaped
casing having an accommodation space for accommodating the antenna
unit therein, and a cover body for sealing the accommodation space.
The cover body is provided to any one of four side surfaces of the
casing or one main surface having the largest width of the casing,
and seals the accommodation space.
[0135] FIG. 1A illustrates an example of a shape of the case body.
FIG. 1B is a cross-sectional view of one side portion (a vertical
side L1 in this example) of FIG. 1A. A case body 10 is an example
of a case having a vertical side L1 of about 90 mm, a horizontal
side L2 of about 90 mm, and a depth L3 of about 13 mm. As
illustrated in FIG. 1B, the case 10 is in an internal size of about
87 mm in inner side L11 of the vertical side L1, and about 10 mm in
inner depth L31. The case body is sealed with the cover body after
the antenna unit is accommodated in the case body. On a mounting
portion of the case body, one of plural prepared holding parts (not
illustrated) is mounted according to a shape on a plane of a
dashboard, for example.
[0136] The antenna unit to be accommodated in the case body 10 will
he described. FIGS. 2A to 2D each are a diagram illustrating a
configuration example of the antenna unit. FIG. 2A is a front view,
FIG. 2B is a rear view of FIG. 2A, FIG. 2C is a top view, and FIG.
2D is a perspective view. For convenience, an orthogonal coordinate
system including x, y, and z axes is defined. The antenna unit
includes a pair of first elements that are arranged on a first
plane 100, and a pair of second elements that are arranged on a
second plane 200 parallel to the first plane 100 so that a
polarized wave direction of the pair of second elements is
orthogonal to that of the pair of first elements, Each
configuration of the pair of first elements and the pair of second
elements will be described with reference to FIGS. 3A and 3B.
[0137] A predetermined portion teach element (in the illustrated
example, portions on the respective pair of first elements that are
closest to each other and portions on the respective pair of second
elements that are closest to each other) is a portion to which a
feed point is connectable. Such a portion is referred to as a
"proximal end, portion." When it is particularly necessary to
distinguish between proximal end portions of the pair of first
elements and proximal end portions of the pair of second, elements,
the former may be referred to as "first proximal end portions," and
the later may be referred to as "second proximal end portions," One
of the pair of first elements (for convenience, referred to as "one
first element") includes two arms 101a and 102a that extend in a
direction away from the corresponding first proximal end portion,
and open end portions are formed at respective distal ends of the
arms 101a and 102a.
[0138] The other of the pair of first elements (for convenience,
referred to as "the other first element") also includes two arms
101b and 102b that extend in a direction away from the
corresponding first proximal end portion, and open end portions are
formed at respective distal ends of the arms 101b and 102b. Each of
the two arms (for example, 101a and 102a) included in the one first
element has a width that is continuously or gradually increased as
being away from the first proximal end portion. That is, each width
is larger in a region far from the first proximal end portion than
in a region close to the first proximal end portion. Additionally,
a facing distance between the two arms is continuously or gradually
increased as being away from the first proximal end portion. That
is, the facing distance between the two arms is larger in the
region far from the first proximal end portion than in the region
close to the first proximal end portion. This is to cause the arms
101a and 102a to act as a self-similarity antenna such as a
biconical antenna or a bow-tie antenna or an antenna that acts
based on similar operating principle to the self-similarity
antenna
[0139] The similar applies to the two arms (for example, 101b and
102b) of the other first element. Additionally, the two arms (for
example, 101a and 102a) included in the one first element extend in
directions away from each other from the two arms (for example,
101b and 102b) included in the other first element.
[0140] The pair of second elements have shape and structure similar
to those of the pair of first elements. That is, one of the pair of
second elements (for convenience, referred to as "one second
element") includes two arms 201a and 202a that extend in a
direction away from the corresponding second proximal end portion,
and open end portions are formed at respective distal ends of the
arms 201a and 202a. Each of the two arms (for example, 201a and
202a) included in the one second element has a width that is
continuously or gradually increased as being away from the second
proximal end portion. That is, each width is larger in a region far
from the second proximal end portion than in a region close to the
second proximal end portion. Additionally, a facing distance
between the two arms is continuously or gradually increased as
being away from the second proximal end portion. That is, the
facing distance between the two arms is larger in the region far
from the second proximal end portion than in the region close to
the second proximal end portion. This is to cause the arms 201a and
202a to act as a self-similarity antenna such as a biconical
antenna or a bow-tie antenna or an antenna that acts based on
similar operating principle to the self-similarity antenna. The
similar applies to two arms (for example, 201b and 202b) of the
other second element. Additionally, the two arms (for example, 201a
and 202a) included in the one second element extend in directions
away from each other from the two arms (for example, 201b and 202b)
included in the other second element.
[0141] Next, arrangements of the pair of first elements and the
pair of second elements will be described. A midpoint of a distance
between the first proximal end portion of the one first element and
the first proximal end portion of the other first element is
referred to as a first center portion. Additionally, an approximate
midpoint of a distance between the second proximal end portion of
the one second element and the proximal end portion of the other
second element is referred to as a second center portion. The first
center portion is a feed point K1 for the first elements, and the
second center portion is a feed point K2 for the second elements.
The first center portion and the second center portion overlap each
other when viewed from the plane (for example, the front side or
the rear side).
[0142] The pair of second elements are arranged to face the pair of
first elements in a state in which the pair of second elements are
turned by approximately 90 degrees from a position at which a
second center portion is aligned with the first center position
while maintaining a space D11. Therefore, split rings (each having
a ring shape in which a portion thereof is cut so that the split
portions face each other) are formed between the first elements and
the second elements facing one another. The polarized wave
direction of the first elements is orthogonal to that of the second
elements. That is, for example, when the polarized wave direction
of the first elements is perpendicular (perpendicularly polarized
wave), the polarized wave direction of the second elements is
horizontal (horizontally polarized wave). Conversely, when the
polarized wave direction of the first elements is horizontal
(horizontally polarized wave), the polarized wave direction of the
second elements is perpendicular (perpendicularly polarized
wave).
[0143] The term "approximately 90 degrees" means that it is not
necessarily strictly 90 degrees.
[0144] A size obtained by connecting outer edges (outer edge size)
of the first elements is similar to an outer edge size of the
second elements. Therefore, the outer edge size is the same before
and after turning of the pair of second elements. Each element is,
for example, a conductive plate having a thickness of 0.5 mm, and
the outer edge size is a size enough to be accommodated in the
accommodation space of the case body 10 illustrated in FIG. 1. In
one example, the outer edge size of each element is about 87
mm.times.about 87 mm.times.about 10 mm. The space DU between the
first plane 100 and the second plane 200 corresponds to an inner
depth L31 of the above-described case body 10, that is, is about 9
mm.
[0145] Next, each element structure of the pair of first elements
and the pair of second elements will be described in detail. FIGS.
3A and 3B each are a diagram illustrating a structure example of
the second elements. The pair of second elements are configured as
illustrated in FIG. 3B, by joining or integrally forming the two
arms 201a and 202a included in the one second element and the two
arms 201b and 202b included in the other second element
symmetrically about the second proximal end portions (feed point
K2) as illustrated in FIG. 3A.
[0146] A portion from each of the arms 201a, 202a, 201b, and 202b
to the corresponding distal end is an open end. The portion of the
distal end is referred to as an "open end portion." Each open end
portion is formed so that the first element and the second element
each mainly have a certain area or more to secure a low frequency
band (to allow use in a lower frequency band). In this example, the
open end portion is formed in ant, shape. However, the shape of the
open end portion is not limited to an L shape, and may be a
trapezoid, a rhombus, an oval, a circle, a triangle, or the
like.
[0147] Each of the two arms 201a and 202a included in the one
second element and the two arms 201b and 202b included in the other
second element has a width that is continuously or gradually
increased in a region from the corresponding second. proximal end
portion to the corresponding open end portion, as being away from
the corresponding second proximal end portion. That is, each of the
two arms 201a and 202a included in the one second element and the
two arms 201b and 202b included in the other second element is
configured so that the width is larger in a region far from the
corresponding second proximal end portion and close to the
corresponding open end portion than in a region close to the
corresponding second proximal end portion and far from the
corresponding open end portion. Additionally, the facing distance
between the two arms 201a and 202a included in the one second
element and the facing distance between the two arms 201b and 202b
included in the other second element are continuously or gradually
increased as being away from the respective second proximal end
portions. That is, each of the facing distance between the two arms
201a and 202a included in the one second element and the facing
distance between the two arms 201b and 202b included in the other
second element is larger in the region far from the corresponding
second proximal end portion than in the region close to the
corresponding second proximal end portion. Such a configuration
enables the second elements to act as a self-similarity antenna
such as a biconical antenna or a bow-tie antenna or an antenna that
acts based on similar operating principle to the self-similarity
antenna. In this way, the two arms 201a and 202a included in the
one second element and the two arms 201b and 202b included in the
other second element form substantially V shapes, respectively,
together with the respective second proximal end portions.
[0148] The pair of first elements also have the element structure
similar to that in FIGS. 3A and 3B.
[0149] FIGS. 4A to 4C each show antenna characteristics in the case
where the one second element (for example, the two arms 201a and
202a) of FIG. 3A is used alone as an antenna. FIG. 4A is a graph
showing a VSWR characteristic, FIG. 4B is a graph showing a
radiation efficiency characteristic, and FIG. 4C is a graph showing
an average gain characteristic in a horizontal plane (x-y plane) of
the antenna of FIG. 3A. In each of the graphs, the horizontal axis
represents a frequency (MHz). The average gain is an average gain
in the horizontal plane (the similar shall apply hereinafter). As
shown in FIGS. 4A and 4B, when only the second element is used
alone as an antenna, an operation as a resonant antenna is dominant
in the vicinity of about 900 MHz, and an operation as a
non-resonant antenna is dominant at about 2500 MHz or more. As can
he seen in FIG. 4C, the average gain is about -2 dBi or more in a
frequency band of about 900 MHz to 4500 MHz, which is in a
practically usable level comparable to the MEM antenna device
disclosed in Patent Literature 1.
[0150] FIGS. 5A to 5C show antenna characteristics in the case
where the pair of second elements illustrated in FIG. 3B are acted
as antennas. FIG. 5A is a graph showing a VSWR characteristic, FIG.
5B is a graph showing a radiation efficiency characteristic, and
FIG. 5C is a graph showing an average gain characteristic in the
horizontal plane (x-y plane) of the antenna of FIG. 3B. In each of
the graphs, the horizontal axis represents a frequency (MHz). As
can be seen in FIGS. 5A to 5C, in the case where the pair of second
elements are acted as antennas, the VSWR, the radiation efficiency,
and the average gain (dBi) in the vicinity of a frequency of about
1500 MHz are more significantly improved than the case where one
second element illustrated in FIG. 3A is used. The similar antenna
characteristics can be obtained with respect to the pair of first
elements.
[0151] Next, the antenna characteristics of the antenna unit
configured as illustrated in FIGS. 2A to 2D will be described. In
the antenna unit, the pair of second elements face the pair of
first elements in a state in which the pair of second elements are
turned by approximately 90 degrees from a position at which the
second proximal end portions are aligned with the first proximal
end portions while maintaining the space D11. That is, the split
rings are formed between the first elements and the second elements
facing one another. Therefore, the frequency band expands to the
low frequency side, whereby the antenna unit can act as a broadband
antenna. The polarized wave of the first elements is orthogonal to
that of the second elements. For example, when the polarized wave
of the first elements is a perpendicularly polarized wave, the
polarized wave of the second elements is a horizontally polarized
wave. Conversely, when the polarized wave of the first elements is
a horizontally polarized wave, the polarized wave of the second
elements is a perpendicularly polarized wave. Therefore, the mutual
interference can be reduced. For example, the isolation can he more
significantly improved than the case where the second proximal end
portions are not turned.
[0152] Hereinafter, the characteristic example of the antenna unit
of the first embodiment will be specifically described. FIG. 6A is
a graph showing a VSWR. characteristic of the feed point K1, and
FIG. 6B is a graph showing a VSWR. characteristic of the feed point
K2. In each of the graphs, the horizontal axis represents a
frequency (MHz). According to the antenna unit of the first
embodiment, an available frequency band of a reception wave or a
transmission wave expands to the low frequency side.
[0153] FIG. 7A is a graph showing a radiation efficiency
characteristic of the feed point K1, and FIG. 7B is a graph showing
a radiation efficiency characteristic of the feed point K2. In each
of the graphs, the horizontal axis represents a frequency (MHz). In
the antenna unit of the first embodiment, the radiation efficiency
in the vicinity of 698 MHz is about 0.85 (in the example of FIG.
4B, about 0.17, and in the example of FIG. 5B, about 0.3). It is
found that the available frequency expands in the lower frequency
direction.
[0154] FIG. 8A is a graph showing a passing power characteristic
from the feed point K1 to the feed point K2, and. FIG. 8B is a
graph showing a passing power characteristic from the feed point K2
to the feed point K1. The vertical axis of FIG. 8A represents 20
Log|S21| (dB), the vertical axis of FIG. 8B represents 20 Log|S12|
(dB), and each horizontal axis of FIGS. 8A and 8B represents a
frequency (MHz). "S21" is an S parameter representing a
transmission coefficient from the feed point K1 for the first
elements to the feed point K2 for the second elements, and "20
Log|S21|" represents the passing power characteristic in decibels.
Additionally, "S12" is an S parameter representing a transmission
coefficient from the feed point K2 for the second elements to the
feed point K1 for the first elements, and "20 Log|S12|" represents
the passing power characteristic in decibels.
[0155] In the antenna unit of the first embodiment, the isolation
between the feed point K1 and the feed point K2 is about -30 dB to
about -70 dB or less over a wide frequency band from 698 MHz and
frequencies before and after 698 MHz to about 6 GHz and frequencies
equal to or more than about 6 GHz. That is, the interference
between the antennas is extremely small while the feed point K1 and
the feed point K2 are close to each other.
[0156] The antenna unit of the first embodiment is installed on the
z-plane that extends vertically upward with respect to the x-y
plane parallel to the ground, but the present inventors have
verified how much the antenna characteristics change when the
antenna unit is inclined by a predetermined angle on the
z-plane.
[0157] FIG. 9A is a front view of the antenna unit of the
embodiment, and is the same as FIG. 2A. FIG. 9B is a diagram
illustrating a state in which the antenna. unit is inclined by a
predetermined angle .theta., for example, by approximately 45
degrees in the counterclockwise direction. FIG. 10A is a graph
showing an average gain characteristic in the horizontal plane (x-y
plane) of the feed point K1 in the arrangement of FIG. 9A. FIG. 10B
is a graph showing an average gain characteristic in the horizontal
plane (x-y plane) of the feed point K2 in the arrangement of FIG.
9A. In each of the graphs, the vertical axis represents an average
gain (dBi), and the horizontal axis represents a frequency (MHz).
In the pair of first elements, for example, the average gain in the
vicinity of 698 MHz is about 1 dBi, and for example, the average
gain in the vicinity of 6 GHz is about -3 dBi. The gain variation
within the above-described frequency range is smaller than that
shown in FIGS. 4C and 5C. In the pair of second elements, for
example, the average gain in the vicinity of 698 MHz is about -2
dBi, and for example, the average gain in the vicinity of 6 GHz is
-2 dBi. The average gain variation within the above-described
frequency range is also smaller than that shown in FIGS. 4C and
5C.
[0158] FIG. 11A is a graph showing an average gain characteristic
in the horizontal plane (x-y plane) of the feed point K1 when the
antenna unit is inclined, that is, in a state of FIG. 9B. FIG. 11B
is a graph showing an average gain characteristic in the horizontal
plane (x-v plane) of the feed point K2 in a state of FIG. 9B. As
compared with FIGS. 10A and 10B, in both of the first elements and
the second elements, the gain in the frequency band of 5 GHz or
more is higher than that before turning of the antenna unit.
Additionally, the difference between the maximum value and the
minimum value of the gain is about 6 dB before turning of the
antenna. unit, whereas it is reduced to about 4 dB in the turned
state. That is, it is found that when the antenna unit is inclined
by approximately 45 degrees and fixed, the average gain variation
can be reduced while increasing the average gain.
[0159] The term "approximately 45 degrees" means that it is not
necessarily strictly 45 degrees.
[0160] Here, to describe the characteristic operation of the
antenna unit of the first embodiment, an antenna unit in a
comparative example which has a structure similar to that of the
antenna unit of the first embodiment will be described. FIG. 12A is
a front view of the antenna unit of the comparative example, FIG.
12B is a rear view of the antenna unit of the comparative example,
FIG. 12C is a top view of the antenna unit of the comparative
example, and FIG. 12D is a perspective view of the antenna unit of
the comparative example. The antenna unit of the comparative
example includes a pair of first bow-tie antennas and a pair of
second bow-tie antennas, each which has the same frequency,
material, and longitudinal and lateral sizes as the antenna unit of
the first embodiment. The size is a size enough to be accommodated
in the case body 10 illustrated in FIG. 1.
[0161] The pair of first bow-tie antennas 501 and 502 having a
semicircular plate shape are arranged on a first plane 500 so that
respective diameter portions thereof face outwardly. The pair of
second bow-tie antennas 601 and 602 having a semicircular plate
shape are arranged on a second plane 600 so that respective
diameter portions thereof face outwardly. The bow-tic antennas are
arranged to face the other bow-tie antennas in a state in which the
other bow-tie antennas are turned by approximately 90 degrees from
a position at which arc portions in which the other bow-tie
antennas are closest to each other (for example, arc portions to
which the feed point K2 is connected) are aligned with arc portions
in which the bow-tie antennas are closest to each other (for
example, arc portions to which the feed point K1 is connected)
while maintaining the space D11.
[0162] FIG. 13A is a graph showing a VSWR. characteristic of the
antenna unit of the comparative example, and FIG. 13B is an
enlarged graph showing a low frequency portion of FIG. 13A. FIG.
14A is a graph showing a radiation efficiency characteristic of the
antenna unit of the comparative example, and FIG. 14B is an
enlarged graph showing a low frequency portion of FIG. 14A. In each
of the graphs, the horizontal axis represents a frequency (MHz).
The measurement conditions for each characteristic are similar to
those of the antenna unit of the first embodiment. A broken line in
each graph represents the characteristics in the case where only
the pair of first bow-tie antennas 501 and 502 are used, and a
solid line in each graph represents the characteristics in the case
where the pair of first bow-tie antennas 501 and 502 and the pair
of second bow-tie antennas 601 and 602 face each other.
[0163] These measurement results show that even only the pair of
bow-tie antennas (for example, the first bow-tie antennas 501 and
502) can be used as broadband antennas, and that reduction in the
VSWR and the radiation efficiency may be unable to be prevented
only by arranging one pair of bow-tie antennas and the other pair
of bow-tie antennas to face each other in a state in which the
other bow-tie antennas are turned by approximately 90 degrees from
a. position at which the arc portions in which the other pair of
bow-tie antennas are closest to each other are aligned with the arc
portions in which the one bow-tie antennas are closest to each
other while maintaining the space D11. In particular, in the low
frequency band, the VSWR is minimized near 1000 MHz, and
specifically, is about 6. The radiation efficiency becomes 0.5 or
less.
Second Embodiment
[0164] Next, a second embodiment of the present invention will be
described. An antenna unit of the second embodiment is similar to
the antenna unit of the first embodiment in that a pair of first
elements and a pair of second elements are provided, in which
respective polarized wave directions are orthogonal to each other,
and each element includes a portion that acts as a self-similarity
antenna, but is different from the antenna unit of the first
embodiment in the shape and structure of each element. However, the
antenna unit of the second embodiment has a size similar to the
antenna unit of the first embodiment. That is, the case body 10
illustrated in FIG. 1 can also accommodate the antenna unit of the
second embodiment. For the convenience of the description, members
which correspond to the members of the antenna unit of the first
embodiment are described by using the same member names and
denoting the same reference numerals thereto.
[0165] FIG. 15A is a front view of the antenna unit according to
the second embodiment, FIG. 15B is a rear view of the antenna unit
according to the second embodiment, FIG. 15C is a top view of the
antenna unit according to the second embodiment, and FIG. 15D is a
perspective view of the antenna unit according to the second
embodiment. The antenna unit of the second embodiment includes a
pair of first elements and a pair of second elements. The pair of
second elements face the pair of first elements in a state in which
the pair of second elements are turned by approximately 90 degrees
from a position at which a second center portion (a portion or port
to which a feed point K2 is connected) is aligned with a first
center portion (a portion or port to which a feed point K1 is
connected) while maintaining a space D11. The outer edge size of
the antenna unit is the same before and after turning of the second
elements.
[0166] The pair of first elements will be described. One first
element includes two arms 101c and 101d that extend in a direction
away from each other from a first proximal end portion thereof. The
other first element also includes two arms 102c and 102d that
extend in a direction away from each other from a first proximal
end portion thereof. The arm 101c of the one first element extends
in a direction away from the arm 102c of the other first element
that is closest to the arm 101c. The arm 101d also extends in a
direction away from the arm 102d in the similar manner. Each of the
one first element and the other first element is arranged
symmetrically about a first center portion, and is formed in a
substantially C shape when viewed from the front side.
[0167] Each of the arms 101c, 101d, 102c, and 102d is a conductive
plate having a uniform width, and a distal end thereof is an open
end portion that is formed in a predetermined shape, for example,
an 1, shape. The open end portion of the arm 101c and the open end
portion of the arm 101d face each other, and the open end portion
of the arm 102c and the open end portion of the arm 102d face each
other. Additionally, bent regions 1011c, 1011d, 1021c, and 1021d
are formed in parts of the respective open end portions. Each of
the bent regions 1011c, 1011d, 1021c, and 1021d is formed by being
bent by approximately 90 degrees in a thickness direction of the
antenna unit, that is, a direction toward the second elements which
will be described later. This is to reduce the overall size while
maintaining the performance.
[0168] The pair of second elements will be described. One second
element includes two arms 201c and 201d that extend in a direction
away from each other from a second proximal end portion thereof.
The other second element also includes two arms 202c and 202d that
extend in a direction away from each other from a second proximal
end portion thereof. The arm 201c of the one second element extends
in a direction away from the arm 202c of the other second element
that is closest to the arm 201c. The arm 201d also extends in a
direction away from the arm 202d in the similar manner. Each of the
one second element and the other second element is arranged
symmetrically about a second center portion, and is formed in a
substantially C shape when viewed from the front side.
[0169] Each of the arms 201c, 201d, 202c, and 202d is a conductive
plate having a uniform width, and a distal end thereof is an open
end portion that is formed in a predetermined shape, for example,
an L shape. The open end portion of the arm 201c and the open end
portion of the arm 201d face each other, and the open end portion
of the arm 202c and the open end portion of the arm 202d face each
other. Additionally, bent regions 2011c, 2011d, 2021c, and 2021d
are formed in parts of the respective open end portions. Each of
the bent regions 2011c, 2011d, 2021c, and 2021d is formed by being
bent by approximately 90 degrees in a thickness direction of the
antenna unit, that is, a direction toward the first elements. This
is to reduce the overall size while maintaining the
performance.
[0170] Similarly to the antenna unit of the first embodiment, also
in the antenna unit of the second embodiment, split rings are
formed, whereby an available frequency band can expand to the low
frequency side.
[0171] FIGS. 16A to 19B each show antenna characteristics of the
antenna unit of the second embodiment. FIG. 16A is a graph showing
a VSWR. characteristic of a feed point K1, and FIG. 16B is a graph
showing a VSWR characteristic of a feed point K2. FIG. 17A is a
graph showing a radiation efficiency characteristic of the feed
point K1, and FIG. 17B is a graph showing a radiation efficiency
characteristic of the feed point K2. In each of the graphs, the
horizontal axis represents a frequency (MHz). Additionally, FIG.
18A is a graph showing a passing power characteristic from the feed
point K1 for the first elements to the feed point K2 for the second
elements, and FIG. 18B is a graph showing a passing power
characteristic from the feed point K2 for the second elements to
the feed point K1 for the first elements. The vertical axis of FIG.
18A represents 20 Log|S12| (dB) described above, the vertical axis
of FIG. 18B represents 20 Log|S12| (dB), and each horizontal axis
of FIGS. 18A and 18B represents a frequency (MHz). FIG. 19A is a
graph showing an average gain characteristic in a horizontal plane
(x-y plane) of the feed point K1 in the arrangement of FIG. 15A.
FIG. 19B is a graph showing an average gain characteristic in the
horizontal plane (x-y plane) of the feed point K2 in the
arrangement of FIG. 15A. In each of the graphs, the horizontal axis
represents a frequency (MHz).
[0172] The bent regions 1011c, 1011d, 1021c, 1021d, 2011c, 2011d,
2021c, and 2021d may be provided in the antenna unit of the first
embodiment. It is confirmed that when the antenna unit of the
second embodiment is inclined by approximately 45 degrees and fixed
on the Z surface as illustrated in FIG. 158, the average gain in
the horizontal plane (x-y plane) is stably increased.
Third Embodiment
[0173] Next, a third embodiment of the present invention will be
described. An antenna unit of the third embodiment is similar to
the antenna units of the first embodiment and the second embodiment
in that a pair of first elements and a pair of second elements are
provided, in which respective polarized wave directions are
orthogonal to each other, and each element includes a portion that
acts as a self-similarity antenna or an antenna that acts based on
similar operating principle to the self-similarity antenna, but is
different from the antenna unit of the first embodiment in the
shape and structure of each element.
[0174] As one of the features, in the antenna unit of the third
embodiment, the first element and the second element are different
from each other in shape, structure. and size. The outer edge size
of the antenna unit is formed in a rectangular shape when viewed
from the front side. Therefore, the antenna unit has long side
portions and short side portions. The antenna case 10 illustrated
in FIGS. 1A and 1B has a rectangular parallelepiped shape in which
the long side portion is relatively long.
[0175] However, for the convenience of the description, members
which correspond to the members of the antenna units of the first
embodiment and the second embodiment are described by using the
same member names and denoting the same reference numerals
thereto.
[0176] FIG. 20A is a front view of the antenna unit according to
the third embodiment, FIG. 20B is a side view of the long side
portion of the antenna unit according to the third embodiment, FIG.
20C is a side view of the short side portion of the antenna unit
according to the third embodiment, and FIG. 20D is a perspective
view of the antenna unit according to the third embodiment.
[0177] The antenna unit of the third embodiment includes a pair of
first elements and a pair of second elements. The pair of second
elements face the pair of first elements in a state in which the
pair of second elements are turned by approximately 90 degrees from
a position at which a second center portion (a portion or port to
which a feed point K2 is connected) is aligned with a first center
portion (a portion or port to which a feed point K1 is connected)
while maintaining a predetermined space. The predetermined space is
the same as the space D11 described in the first embodiment.
[0178] The pair of first elements will be described. One first
element includes two arms 101c and 101d that extend in a direction
away from each other from a first proximal end portion thereof. The
other first element includes two arms 102c and 102d that extend in
a direction away from each other from a first proximal end portion
thereof. Each of the two arms 101c and 101d included in the one
first element and the two arms 102c and I 02d included in the other
first element has a width that is continuously or gradually
increased as being away from the corresponding first proximal end
portion. That is, each width of the two arms 101c and 101d included
in the one first element and the two arms 102c and 102d included in
the other first element is larger in a region far from the
corresponding first proximal end portion than in a region close to
the corresponding first proximal end portion. Additionally, a
facing distance between the one first element and the other first
element is continuously or gradually increased as being away from
the first proximal end portions. That is, the facing distance
between the one first element and the other first element is larger
in the region far from the first proximal end portions than in the
region close to the first proximal end portions. The arm 101c of
the one first element extends in a direction away from the arm 102c
of the other first element that is closest to the arm 101c. Such a
configuration enables the first elements to act as a
self-similarity antenna such as a biconical antenna or a bow-tie
antenna or an antenna that acts based on similar operating
principle to the self-similarity antenna.
[0179] Open end portions are formed at respective distal end
portions of the arms 101c, 101d, 102c, and 102d. Each open end
portion is formed in a predetermined shape, for example, an L
shape. The open end portion of the arm 101c and the open end
portion of the arm 101d face each other, and the open end portion
of the arm 102c and the open end portion of the arm 102d face each
other. In this way, each of the pair of two arms 101c and 101d
included in the one first element and the pair of arms 102c and
102d included in the other first element is arranged symmetrically
about a first center portion, and is formed in a substantially C
shape when viewed from the front side.
[0180] Next, the pair of second elements will be described. Each of
a facing distance between the two anus 201c and 202c included in
the one second element and a facing distance between the two arms
201d and 202d included in the other second element is continuously
or gradually increased as being away from the corresponding second
proximal end portion. That is, each of the facing distance between
the two arms 201c and 202c included in the one second element and
the facing distance between the two arms 201d and 202d included in
the other second element is larger in the region far from the
corresponding second proximal end portion than in the region close
to the corresponding second proximal end portion. The arm 201c of
the one second element extends in a direction away from the arm
201d of the other second element that is closest to the arm 201c.
In this way, each of the facing distance between the arms 201c and
202c and the facing distance between the arms 201d and 202d is
larger in a region in the vicinity of the open end portions than in
a region in the vicinity of the proximal end portion. Such a
configuration enables the second elements to act as a
self-similarity antenna such as a. biconical antenna or a bow-tie
antenna or an antenna that acts based on similar operating
principle to the self-similarity antenna.
[0181] In this way, each of the pair of two arms 201c and 202c
included in the one second element and the pair of arms 201d and
202d included in the other second element is arranged symmetrically
about a second center portion, and is formed in a substantially C
shape when viewed from the front side.
[0182] Open end portions are formed at respective distal end
portions of the arms 201c, 201d, 202c, and 202d, A change rate of
the width from the region in the vicinity of the second proximal
end portion to the region in the vicinity of the open end portion
in each of the arms 201c, 201d, 202c, and 202d is smaller than the
change rate of the width from the region in the vicinity of the
first proximal end portion to the region in the vicinity of the
open end portion in the first element. A bent region 2011c in the
long side and a bent region 2012c in the short side are formed in a
part of the open end portion of the arm 201c. The bent region 2011c
in the long side is formed by being bent by 90 degrees in the
thickness direction of the antenna unit, that is, a direction
toward the first element that is closest to the bent region 2011c.
The bent region 2012c in the short side is formed by being bent by
90 degrees in a direction from the bent region 2011c in the long
side toward the other first element.
[0183] Also in each open end portion of the other arms 202c, 201d,
and 202d, the bent regions having the same structure as the open
end portion of the arm 201c are formed. That is, a bent region
2021c. in the long side and a bent region 2022c in the short side
are formed in a part of the arm 202c. A bent region 2011d in the
long side and a bent region 2012d in the short side are formed in a
part of the arm 201d. A bent region 2021d in the long side and a
bent region 2022d in the short side are formed in a part of the arm
202d.
[0184] When these bent regions 2011c, 2012c, 2021c, 2022c, 2011d,
2012d, 2021d, and 2022d are formed, the overall size can be reduced
while maintaining the antenna performance that is obtained in the
case where these bent regions are not formed. Additionally, the
split rings are formed using the pair of first elements and the
pair of second elements, whereby an available frequency band can
expand to the low frequency side.
[0185] FIGS. 21A to 24B each show antenna characteristics of the
antenna unit of the third embodiment. FIG. 21A is a graph showing a
VSWR characteristic of a feed point K1, and FIG. 21B is a graph
showing a VSWR characteristic of a feed point K2. FIG. 22A is a
graph showing a radiation efficiency characteristic of the feed
point K1, and. FIG. 22B is a graph showing a radiation efficiency
characteristic of the feed point K2. In each of the graphs, the
horizontal axis represents a frequency (MHz). Additionally, FIG.
23A is a graph showing a passing power characteristic from the feed
point K1 for the first elements to the feed point K2 for the second
elements, and FIG. 23B is a graph showing a passing power
characteristic from the feed point K2 for the second elements to
the feed point K1 for the first elements. The vertical axis of FIG.
23A represents 201.og521 (dB), the vertical axis of FIG. 23B
represents 20 Log|S12| (dB), and each horizontal axis of FIGS. 23A
and 23B represents a frequency (MHz). FIG. 24A is a graph showing
an average gain characteristic in a horizontal plane (x--y plane)
of the feed point K1 in the arrangement of FIG. 20A. FIG. 24B is a
graph showing an average gain characteristic in the horizontal
plane (x-y plane) of the feed point K2 in the arrangement of FIG.
20A. In each of the graphs, the horizontal axis represents a
frequency (MHz).
Fourth Embodiment
[0186] Next, a fourth embodiment of the present invention will be
described. An antenna unit of the fourth embodiment is similar to
the antenna unit of the first embodiment in that a pair of first
elements and a pair of second elements are provided, in which
respective polarized wave directions are orthogonal to each other,
and each element includes a portion that acts as a self similarity
antenna or an antenna that acts based on similar operating
principle to the self-similarity antenna, but is different from the
antenna unit of the first embodiment in the shape and structure of
each element. However, for the convenience of the description,
members which correspond to the members of the antenna units of the
first embodiment are described by using the same member names and
denoting the same reference numerals thereto.
[0187] FIG. 25A is a front view of the antenna unit according to
the fourth embodiment, FIG. 25B is a top view of the antenna unit
according to the fourth embodiment, and FIG. 25C is a perspective
view of the antenna unit according to the fourth embodiment. The
antenna unit of the fourth embodiment has a basic structure similar
to the antenna unit of the first embodiment. A space between the
pair of first elements and the pair of second elements, and an
outer edge size of the pair of first elements and the pair of
second elements are similar to the antenna unit of the first
embodiment.
[0188] The antenna unit of the fourth embodiment is different from
the antenna unit of the first embodiment in that each open end
portion of arms included in the first elements is conductively
connected to one of open end portions of arms included in the
second elements that is closest to the above-described open end
portion of the first element, and each open end portion of the arms
included in the first elements and the corresponding open end
portion of the second element are formed integrally with each
other, thereby being formed in a loop shape including a portion
that acts as a self-similarity antenna or an antenna that acts
based on similar operating principle to the self-similarity
antenna. Therefore, in the antenna unit according to the fourth
embodiment, the above-described split rings are not formed.
[0189] FIGS. 26A to 29B each show antenna characteristics of the
antenna unit of the fourth embodiment. FIG. 26A is a graph showing
a VSWR characteristic of a feed point K1, and FIG. 26B is a graph
showing a VSWR characteristic of a feed point K2. FIG. 27A is a
graph showing a radiation efficiency characteristic of the feed
point K1, and FIG. 27B is a graph showing a radiation efficiency
characteristic of the feed point K2. in each of the graphs, the
horizontal axis represents a frequency (MHz). Additionally, FIG.
28A is a graph showing a passing power characteristic from the feed
point K1 for the first elements to the feed point K2 for the second
elements, and FIG. 28B is a graph showing a passing power
characteristic from the feed point K2 for the second elements to
the feed point (dB), the vertical axis of FIG. 28B represents 20
Log|S12| (dB), and each horizontal axis of FIGS. 28A and 28B
represents a frequency (MHz). FIG. 29A is a graph showing an
average gain characteristic in a horizontal plane (x-y plane) of
the feed point KI in the arrangement of FIG. 24A. FIG. 29B is a
graph showing an average gain characteristic in the horizontal
plane (x-y plane) of the feed point K2 in the arrangement of FIG.
24A. In each of the graphs, the horizontal axis represents a
frequency (MHz).
Fifth Embodiment
[0190] Next, a fifth embodiment of the present invention will be
described. An antenna unit of the fifth embodiment is similar to
the antenna unit of the first embodiment in an arrangement relation
between a pair of first elements and a pair of second elements, and
the shape, structure, and size of each element, but is different
from the antenna unit of the first embodiment in how to combine
each of the pairs of elements. Additionally, the forms of the feed
points are embodied. For convenience, members which correspond to
the members of the antenna unit of the first embodiment are
described by using the same member names and denoting the same
reference numerals thereto.
[0191] FIG. 30A is a perspective view illustrating a configuration
example of the antenna unit according to the fifth embodiment, and
FIG. 30B is a perspective view when viewing FIG. 30A from the rear
side. In the first embodiment, the one first element and the other
first element are arranged symmetrically about the first center
portion so that the two elements have a V shape and an inverted V
shape, respectively. However, in the antenna unit of the fifth
embodiment, one of the pair of first elements includes two arms
101a and 101b, and the other first element includes two arms 102a
and 102b, so that the two elements have respective substantially C
shapes formed symmetrically about a first center portion. The
similar applies to the pair of second elements. That is, one second
element includes two arms 201a and 201b, and the other second
element includes two arms 202a and 202b, so that the two elements
have respective substantially C shapes formed symmetrically about a
second center portion.
[0192] Also in such a combination of the elements, a polarized wave
direction of a signal receivable or transmittable by the pair of
first elements is orthogonal to a polarized wave direction of a
signal receivable or transmittable by the pair of second elements,
and each element includes a portion that acts as a self-similarity
antenna or an antenna that acts based on similar operating
principle to the self-similarity antenna. Therefore, the fifth
embodiment can acquire actions and effects similar to those of the
first embodiment.
[0193] Additionally, a first feeder Fl l around which a ferrite
core is wound is connected to a feed point of the first center
portion, and a second feeder F21 around which a ferrite core is
wound at an angle of substantially 90 degrees with respect to the
first feeder F11 is connected to a feed point of the second center
portion. This can prevent leakage currents in the low frequency
range including 698 MHz in which a resonant operation is performed,
and stabilize and improve the radiation characteristic.
[0194] "L11" and "L21" in FIGS. 30A and 30B represent coaxial
cables which are examples of feeders F 11 and F21,
respectively.
MODIFICATION EXAMPLE 1
[0195] In the first, second, fourth, and fifth embodiments, the
description has been made assuming that the first element and the
second element have the same shape, structure and size, but these
embodiments are not limited thereto. When the elements each include
a portion that acts as a self-similarity antenna or an antenna that
acts based on similar operating principle to the self-similarity
antenna, their polarized wave directions are orthogonal to each
other, and an overlapping area between the elements is small, one
of the elements may be different from the other in size.
[0196] In the first, second, fourth, and fifth embodiments, the
description has been made assuming that the pair of first elements
and the pair of second elements each are formed in a substantially
V shape or a substantially C shape, but may he formed in a
substantially D shape, a substantially U shape, a substantially
semicircular shape, a substantially semiellipse shape, a
substantially triangular shape, or a substantially quadrangular
shape. Additionally, in these embodiments, the description has been
made assuming that two feed points are provided, but a
configuration may be adopted in which only one feed point is
provided. Since the first element and the second element are
electrically connected to each other, an operation similar to that
in the case where the two feed points are provided can be
achieved.
[0197] In the first embodiment, an example has been described in
which the antenna characteristics are improved by installing the
antenna unit on the z-plane in a state of being inclined by
approximately 45 degrees. However, also in each of the second to
fifth embodiments, the antenna unit may be installed in a state of
being inclined in the similar manner to the first embodiment. Also
in the case where not only the pair of first elements or the pair
of second elements but also one arm or two arms included in each
element are used as antennas, the antenna unit may be installed by
being inclined in the similar manner.
Effects of Antenna Device According to First to Fifth
Embodiments
[0198] In the antenna unit of each of the first to fifth
embodiments, the pair of first elements and the pair of second
elements are arranged so that the respective polarized wave
directions are orthogonal to each other, whereby the mutual
interference between the elements can be reduced, the antenna
device can be reduced in thickness. Additionally, since each
element of the pair of first elements and the pair of second
elements includes a portion that acts as a self-similarity antenna
or an antenna that acts based on similar operating principle to the
self-similarity antenna, the antenna unit can receive or transmit
the signals over a wide frequency band, and can operate stably over
a wide frequency band.
[0199] Each element of the pair of first elements and the pair of
second elements includes two arms that extend in directions away
from each other from the proximal end portion to which the feed
point is connectable, which enables size reduction of the elements.
As in the antenna unit of the comparative example illustrated in
FIGS. 12A to 12D, in the case where the pair of second bow-tie
antennas 601 and 602 are arranged to face the first bow-tie
antennas 501 and 502 in a state in which the pair of second bow-tie
antennas 601 and 602 are turned by approximately 90 degrees with
respect to a state of being aligned with the pair of first bow-tie
antennas 501 and 502, conductors are generated circumferentially
between the first bow-tie antennas 501 and 502 and the second
bow-tie antennas 601 and 602.
[0200] On the other hand, when the pair of second elements in the
antenna unit 12 of the first to fifth embodiment are arranged to
face the pair of first elements in a state in which the pair of
second elements are turned by approximately 90 degrees with respect
to a state of being aligned with the pair of first elements, an
overlapping area between both elements when being brought close to
each other can be reduced. That is, conductors are not generated
circumferentially between the first elements and the second
elements.
[0201] Accordingly, since scatters are not introduced between both
elements, the reactance variation can be reduced, whereby the
impedance is stabilized. Therefore, a wide frequency band can be
attained.
[0202] Since the antenna unit can be accommodated in a case having
electric wave permeability case body 10) in size of 90 mm in
vertical and horizontal sides and 13 mm in thickness or less, the
interference is reduced while reducing the size and thickness of
the antenna unit, whereby the antenna device in which the two
antennas excellent in isolation are accommodated can be provided.
The antenna device can be also installed, for example, at any place
in a vehicle or at any portion in a room to be used for a MIMO
using a frequency band of LTE or 50.
[0203] Since the antenna unit of the first and second embodiment
has excellent stable antenna characteristics over a frequency band
from a low frequency band to a high frequency band of LTE and 5G,
as shown in FIGS. 6A to 8B and FIGS. 16A to 19B, the antenna unit
of the first and second embodiment can be used as antenna devices
for Japan and foreign countries without need to make any design
changes.
[0204] Since each width is increased as being away from the feed
point K1 (K2), in particular, the VSWR on the high frequency side
can be reduced, the radiation efficiency and the average gain can
be increased, and these variations can be reduced. Since a
configuration is adopted in which the pair of first elements and
the pair of second elements are provided, and the pair of second
elements are arranged to face the pair of first elements in a state
in which the pair of second elements are turned by approximately 90
degrees with respect to a state of being aligned with the pair of
first elements so that both elements are brought close to each
other, each end portion of the first elements and the corresponding
end portion of the second elements facing each other are
electrically connected to each other, to form a loop shape, which
can widen the available frequency band in a direction of a low
frequency in the vicinity of 698 MHz. The antenna device having
such a configuration can expand the available frequency band to the
low frequency side, and further widen the available frequency band,
which would be difficult for the conventional antenna devices, for
example.
[0205] Since the two arms (for example, 101a and 101b) have
respective distal ends that are formed in a predetermined shape
determined according to the shape of the installation position, the
element area required in each arm can be secured while increasing
the flexibility of the element shape. The term "element area
required" is determined according to the resonant frequency of the
split ring expanding the low frequency band.
[0206] Since a portion of a region farthest from the feed point
(for example, K1) in each of the two arms (for example, 101c and
101d) is bent in a direction of the other arms (for example, 201c,
201d) that face the two arms, the frequency band can be expanded to
the low frequency side without Changing sizes of the vertical and
horizontal sides and the thickness of the entire antenna unit (and
the case body 10),
[0207] In the antenna unit of the comparative example described in
the first embodiment, in the case where each of the pair of bow-tie
antennas and the other pair of bow-tie antennas that are arranged
at approximately 90 degrees with respect to each other is used as a
broadband antenna while being spaced apart from each other by 40 mm
or more, the antenna characteristics of a practical level can be
obtained.
[0208] In the first to fifth embodiments, the description has been
made assuming that the minimum frequency in the LTE is 698 MHz.
However, in the case where the available frequency is expanded to
the low frequency side up to about 450 MHz while maintaining the
performance of the antenna of each embodiment, such expansion can
be implemented by increasing the size (outer edge size) when
viewing the antenna unit from the front side or rear side according
to the ratio of the wavelength, without changing the space D11 of
the antenna unit. Although being inferior to the performance of the
antenna unit of each embodiment, the available frequency can be
expanded to the low frequency side up to about 450 MHz by providing
appropriate width of each arm and appropriate area of a portion
corresponding to each open end portion without changing the size
(outer edge size) of the antenna unit.
Sixth Embodiment
[0209] Next, a sixth embodiment of the present invention will be
described. In the sixth embodiment, the description will be made
about an antenna unit having a configuration designed in
consideration of the simplification of a creation process of the
elements in addition to the actions and effects of the antenna unit
of each of the first to fifth embodiments. The antenna unit of the
sixth embodiment is generally similar to the antenna unit of the
first to fifth embodiment in providing a pair of first elements and
a pair of second elements, an arrangement relation between these
elements, and a feeding system. For convenience, members which
correspond to the members of the antenna unit of each embodiment
described above are described by using the same member names and
denoting the same reference numerals thereto.
[0210] FIG. 31A is a perspective view of the antenna unit in the
sixth embodiment, FIG. 31B is a front view illustrating a feeding
state of the pair of first elements, and FIG. 31C is a front view
illustrating a feeding state of the pair of second elements. The
antenna unit has a size enough to be accommodated in a box-shaped
resin case (for example, the case 10 illustrated in FIGS. 1A and
1B) having a z-direction length of 60 mm, an x-direction length of
80 mm, and a y-direction length of 15 mm.
[0211] Referring to FIGS. 31A to 31C, one first element of the pair
of first elements includes a proximal end region 101e which is a
first region in which a proximal end portion of the one first
element is formed in a mountain shape in a direction (x-axis
direction) toward a proximal end portion of the other first
element, an extending region 101f which is a second region to be
conductively connected to one end portion of the proximal end
region 101e, and an extending region 101g to be conductively
connected to the other end portion of the proximal end region
101e.
[0212] The other first element also includes a proximal end region
102e in which the proximal end portion of the other first element
is formed in a mountain shape in the direction toward the proximal
end portion of the one first element, an extending region 102f to
be conductively connected to one end portion of the proximal end
region 102e, and an extending region 102g to be conductively
connected to the other end portion of the proximal end region 102e.
The electrical connection can be made by a solder connection or a
conductive via hole. Both regions may be conductively connected to
each other using a conductive screw or bolt and nut, a conductive
adhesive, or a conductive wire.
[0213] The proximal end regions 101e and 102e correspond to partial
regions of arms including portions to which the feed point is to be
connected in the embodiments described above, that is, regions in
the vicinity of the above-described first proximal end portions or
second proximal end portions. The extending regions 101f, 101g,
102f, and 102g correspond to the remaining regions of the
above-described partial regions in the arms in the embodiments
described above.
[0214] After a stripe is printed on each of front and rear surfaces
of one board PB1, the proximal end region 101e, is mutually
conductively connected to the board PBI through a plurality of
conductive via holes 1011e in this example. In this example, the
board PB1 is a printed circuit board (PCB; the same applies
hereinafter) having a substantially rectangular shape. The proximal
end region 102e is also mutually conductively connected to the
board PB1 through a plurality of conductive via holes 1021e after a
stripe is printed on each of the front and rear surfaces of the
board PB1. A portion at which the two proximal end regions 101e and
102e are closest to each other becomes the above-described first
center portion (a portion or port to which a feed point K1 is
connected). A signal line F111 of a coaxial cable F114 as an
example of the feeder is conductively connected to the proximal end
region 102e. A ground line F112 of the coaxial cable F114 is
conductively connected to the proximal end region 101e. This
enables the pair of first elements to act as two dipole antennas.
Additionally, the proximal end region 101e and the extending
regions 101f and 101g, and the proximal end region 102e and the
extending regions 102f and 102g act as two tapered-slot
antennas.
[0215] A ferrite core F113 is attached to the coaxial cable F114,
which can block a current leaking from an outer jacket of the
coaxial cable F114. To increase the gain in the low frequency band
in the vicinity of 698 GHz, the size of the antenna unit is
generally increased. Attaching the ferrite core F113 enables the
size reduction of the antenna unit while securing the gain on the
low frequency side.
[0216] In the coaxial cable F114, a connection point with the first
elements is regarded as the feed point K1, and an end portion
opposite to the feed point K1 is regarded as an output end.
[0217] In general, an impedance matching circuit is mounted on the
printed circuit board, but the antenna of the embodiment does not
require the impedance matching circuit, and the signal line F111
and the ground line F112 of the coaxial cable is directly connected
to the proximal end regions 101e and 102e formed on the board PB1,
respectively. Therefore, a configuration of the entire antenna unit
can be simplified.
[0218] The extending regions 101f, 101g, 102f, and 102g are
substantially perpendicular to the board PB1, have metal plates
having a width in a direction of the second elements, and are each
formed by a sheet metal. Open end portions are formed at portions
in the vicinity of distal ends of the extending regions 101f, 101g,
102f, and 102g, respectively. The open end portions include first
end portions 1011f, 101 1g, 1021f, and 1021g having a trapezoidal
shape on planes perpendicular to the board PB1, and second end
portions 1012f, 1012g, 1022f and 1022g having a substantially
triangular shape on a plane parallel to the board PB1, and being
formed by bending from the respective first end portions. The
objects of forming the second end portions 1012f, 1012g, 1022f, and
1022g in a substantially triangular shape are to maintain a
self-similar shape to keep the impedance constant, whereby the
antenna performance (VSWR, radiation efficiency, gain) is
improved.
[0219] To avoid connection between the second end portions 1012f
and 1012g facing each other and connection between the second end
portions 1022f and 1022g facing each other, the second end portions
1012f, 1012g, 1022f, and 1022g may be formed in a shape close to a
trapezoidal shape 1w culling a part of a tip of the triangular
shape. The width of each end portion is increased toward the distal
end of the corresponding extending region. When the second end
portions 1012f, 1012g, 1022f, and 1022g are formed in a
substantially triangular shape, the entire antenna unit can
continuously maintain the similar shape to keep the impedance
constant, whereby the antenna characteristics, especially, the VSWR
can be improved. The two extending regions 101f and 101g included
in the one first element and the two extending regions 102f and
102g included in the other first element are arranged symmetrically
about the first center portion, and each is formed in a
substantially C shape when viewed from the front side (y-axis
direction).
[0220] Next, the pair of second elements will be described. One
second element of the pair of second elements includes a proximal
end region 201e in which a proximal end portion of the one second
element is formed in a mountain shape in a direction (z-axis
direction) toward a proximal end portion of the other second
element, an extending region 201f to be conductively connected to
one end portion of the proximal end region 201e, and another
extending region 201g to be conductively connected to the other end
portion of the proximal end region 201e. The other second element
also includes a proximal end region 202e in which the proximal end
portion of the other second element is formed in a mountain shape
in the direction toward the proximal end portion of the one second
element, an extending region 202f to be conductively connected to
one end portion of the proximal end region 202e, and another
extending region 202g to be conductively connected to the other end
portion of the proximal end region 202e.
[0221] The proximal end region 201e is formed on a board PB2 that
is arranged on a plane parallel to the board PB1 and is inclined by
about 90 degrees about the first center portion. The board PB2 is a
PCB having a substantially rectangular shape in which the long side
extends in a direction perpendicular to the hoard PB1. The proximal
end region 201e is mutually conductively connected to the board PB2
through a plurality of conductive via holes 2011e after a stripe is
printed on each of front and rear surfaces of the board PB2. The
proximal end region 202e is also mutually conductively connected to
the board PB2 through a plurality of conductive via holes 2021e
after a stripe is printed on each of the front and rear surfaces of
the board PB2.
[0222] A portion at which the two proximal end regions 201e and
202e are closest to each other becomes the above-described second
center portion (a portion or port to which a feed point K2 is
connected). A signal line F211 of a coaxial cable F214 as an
example of the feeder is conductively connected to the proximal end
region 202e. A ground line F212 of the coaxial cable F214 is
conductively connected to the proximal end region 201e. This
enables the pair of second elements to act as two dipole antennas
or two tapered-slot antennas. A ferrite core F213 is attached to
the coaxial cable F214. The effects are similar to the case of the
first elements. Additionally, the proximal end region 201e and the
extending regions 201f and 201g, and the proximal end region 202e
and the extending regions 202f and 202g act as two tapered-slot
antennas,
[0223] In the coaxial cable F214, a connection point with the
second elements is regarded as the feed point K2, and an end
portion opposite to the feed point K2 is regarded as an output
end.
[0224] The extending regions 201f, 201g, 202f, and 202g are
perpendicular to the board PB2, have metal plates having a width in
a direction of the first elements, and are each formed by a sheet
metal. Open end portions are formed at portions in the vicinity of
distal ends of the extending regions 201f, 201g, 202f, and 202g,
respectively. The open end portions include first end portions
2011E, 2011g, 2021f, and 2021g having a trapezoidal shape on planes
perpendicular to the board PB2, and second end portions 2012f,
2012g, 2022f, and 2022g having a substantially triangular shape on
a plane parallel to the board PB2, and being turned by bending from
the respective first end portions. A fact that a part of a tip of
the triangular shape may be cut to form a shape close to a
trapezoidal shape can he also applied to the second elements. The
width of each end portion is increased toward the distal end of the
corresponding extending region. The two extending regions 201f and
201g included in the one second element and the two extending
regions 202e and 202g included in the other second element are
arranged symmetrically about the second center portion, and each is
formed in a substantially C shape when viewed from the front side
(y-axis direction).
[0225] A split ring is formed among the first end portion 1011f,
1011g, 1021f, 1021g and the second end portion 1012f, 1012g, 1022f,
1022g of the first element and the first end portion 2021f, 2021g,
2011f, 2011g and the second end portion 2022f, 2022g, 2012f, 2012g
of the second element which is closest to the first element. That
is, both regions are not conductively connected to each other, but
are capacitively coupled. In this way, the pair of first elements
and the pair of second elements act as a loop antenna, as a whole.
The split ring serves to expand the available frequency band of the
antenna unit to the low frequency side.
[0226] Also in the antenna unit of the sixth embodiment, the pair
of first elements are inclined by approximately 90 degrees with
respect to the pair of second elements, similarly to the antenna
unit of each embodiment described above. Therefore, a polarized
wave direction of a signal receivable or transmittable by the pair
of first elements is orthogonal to a polarized wave direction of a
signal receivable or transmittable by the pair of second elements,
and a part or whole of each element acts as a self-similarity
antenna or an antenna that acts based on similar operating
principle to the self-similarity antenna.
[0227] In the case where each element that acts as a
self-similarity antenna or an antenna that acts based on similar
operating principle to the self-similarity antenna is formed by a
sheet metal, it is required to make the width as narrow as possible
in the vicinity of the proximal end portion to which the feed point
is connected. Therefore, it becomes difficult to form the element
by a sheet metal. However, in the antenna unit of the sixth
embodiment, the proximal end regions 101e and 102e, and the
proximal end regions 201e and 202e are formed by being printed on
the boards PB1 and. PB2, respectively, and the proximal end region
101e, the proximal end region 102e, the proximal end region 201e,
and the proximal end region 202e are conductively connected to the
extending regions 101f and 101g, the extending regions 102f and
102g, the extending regions 201f and 201g, and the extending
regions 202f and 202g, respectively. Therefore, each element can be
easily formed by a sheet metal.
[0228] Additionally, each of the proximal end regions 101e, 102e,
201e, and 202e is configured in which two prints formed on the
front and rear surface of the corresponding one of the boards PB1
and PB2 are conductively connected through the corresponding ones
of the conductive via holes 1011e, 1021e, 2011e, and 2021e.
Therefore, the radiation resistance and the inductance are
increased as compared with the case where each of the proximal end
regions is configured only by one print, and the radiation
efficiency is improved. Partial regions of at least one pair of
elements of the pair of first elements and the pair of second
elements may be formed on the corresponding board PB1, PB2. Each of
the proximal end regions 101e, 102e, 201e, and 202e may he formed
on one side of the corresponding board PB1, PB2. In this case, the
conductive via holes 1011e, 1021e, 2011e, and 2021e are
unnecessary.
[0229] Next, the antenna characteristics of the antenna of the
sixth embodiment will be described.
[0230] FIG. 32A is a graph showing a VSWR characteristic of the
output end of the coaxial cable F114, and FIG. 32B is a graph
showing a VSWR characteristic of the output end of the coaxial
cable F214. FIG. 32C is a graph showing a radiation efficiency
characteristic of the output end of the coaxial cable F114, and
FIG. 32D is a graph showing a. radiation efficiency characteristic
of the output end of the coaxial cable F214. In each of the graphs,
the horizontal axis represents a. frequency (MHz). Additionally,
FIG. 32E is a graph showing a passing power characteristic from the
output end of the coaxial cable F114 to the output end of the
coaxial cable F214, and FIG. 32F is a graph showing a passing power
characteristic from the output end of the coaxial cable F214 to the
output end of the coaxial cable F114. The vertical axis of FIG. 32E
represents 20 Log|S21| (dB), the vertical axis of FIG. 32F
represents 20 Log|S12| (dB), and each horizontal axis of FIGS. 32E
and 32F represents a frequency (MHz). FIG. 32G is a graph showing
an average gain characteristic in a horizontal plane (x-yr plane)
of the output end of the coaxial cable F114 in the arrangement of
FIG. 31A. FIG. 32H is a graph showing an average gain
characteristic in the horizontal plane (x-y plane) of the output
end of the coaxial cable F214. In each of the graphs, the
horizontal axis represents a frequency (MHz).
[0231] As can been understood from these antenna characteristics,
although the antenna unit has an extremely small size having the
z-direction length of less than 60 mm, the x-direction length of
less than 80 mm, and the y-direction length of less than 15 mm, it
can be used and practically used in a low frequency region
including 698 MHz and the frequencies before and after 698 MHz, for
example.
[0232] A configuration in which the antenna unit includes the
proximal end regions formed on the boards and the extending regions
formed 1w a sheet metal and these regions are electrically
connected can be applied to examples other than the example
illustrated in FIGS. 31A to 31C. The above-described configuration
can be also applied to an antenna unit having another configuration
in which one first element and one second element are provided, for
example.
Seventh Embodiment
[0233] In a seventh embodiment, an example will be described in
which each element of an antenna unit is formed by a print on a
board, as an application of the sixth embodiment. FIG. 33A is a
front view of a pair of first elements in the seventh embodiment,
FIG. 33B is a front view of a pair of second elements, FIG. 33C is
a front view illustrating a feeding state of the pair of first
elements, and FIG. 33D is a front view illustrating a feeding state
of the pair of second elements. FIG. 33E is a perspective view for
illustrating the overall state of the first elements and the second
elements, and FIG. 33F is a side view of the antenna unit. A board
is a square-shaped PCB having a thickness of 0.8 trim and a side
length of 87 mm. For convenience, components which are similar to
those of the antenna unit of each embodiment described above are
described by denoting the same reference numerals thereto.
[0234] In the antenna unit of the seventh embodiment, the pair of
first elements are formed by being printed on one side (front
surface) of a board PB3 having planar front and rear surfaces, and
the pair of second elements are formed by being printed on the
other side (rear surface) of the board PB3, in which the polarized
wave direction of the pair of second elements is orthogonal to that
of the pair of first elements.
[0235] Referring to FIG. 33A, one first element of the pair of
first elements includes two arms 101j and 101k that extend in a
direction away from each other from a proximal end portion to which
a feed point is connectable. The arm 101j includes a region 1011j
in which a width is increased as being away from the proximal end
portion, and an open end portion 1012j that is straightly cut from
another corner of the board PB3 to a center portion of the board
PB3. The arm 101k includes a region 1011k in which a width is
increased as being away from the proximal end portion, and an open
end portion 1012k that is straightly cut from one corner of the
board PB3 to the center portion of the board PB3.
[0236] The other first element includes two arms 102j and 102k that
extend in a direction away from each other from a proximal end
portion to which the feed point is connectable. The arm 102j
includes a region 1021j in which a width is increased as being away
from a proximal end portion thereof, and an open end portion 1022j
that is straightly cut from another corner of the board PB3 to the
center portion of the board PB3. The arm 102k includes a region
1021k in which a width is increased as being away from the proximal
end portion, and an open end portion 1022k that is straightly cut
from another corner of the board PB3 to the center portion of the
board PB3. Each element of the pair of first elements acts as a
self-similarity antenna or an antenna that acts based on similar
operating principle to the self-similarity antenna.
[0237] A signal line F111 of the coaxial cable F114 is conductively
connected to the proximal end portion of the one first element, as
illustrated in FIG. 33C. A ground line F112 of the coaxial cable
F114 is conductively connected to the proximal end portion of the
other first element. This enables the pair of first elements to act
as two dipole antennas or two tapered-slot antennas. A ferrite core
F113 is attached to the coaxial cable F114.
[0238] In the coaxial cable F114, a connection point with the first
elements is regarded as a feed point K1, and an end portion
opposite to the feed point K1 is regarded as an output end.
[0239] Referring to FIG. 33B, one second element of the pair of
second elements includes two arms 201j and 201k that extend in a
direction away from each other from a proximal end portion to which
a feed point is connectable. The arm 201j includes a region 2011j
in which a width is increased as being away from the proximal end
portion, and an open end portion 2012j that is straightly cut from
another corner of the board PB3 to a center portion of the board
PB3. The arm 201k includes a region 2011k in which a width is
increased as being away from the proximal end portion, and an open
end portion 2012k that is straightly cut from one corner of the
board PB3 to the center portion of the board PB3.
[0240] The other second element includes two arms 202j and 202k
that extend in a direction away from each other from a proximal end
portion to which the feed point is connectable. The arm 202j
includes a region 2021j in which a width is increased as being away
from a proximal end portion thereof, and an open end portion 2022j
that is straightly cut from another corner of the board PB3 to the
center portion of the board PB3. The arm 202k includes a region
2021k in which a width is increased as being away from the proximal
end portion, and an open end portion 2022k that is straightly cut
from another corner of the board PB3 to the center portion of the
board PB3. Each element of the pair of second elements acts as a
self-similarity antenna. or an antenna that acts based on similar
operating principle to the self-similarity antenna.
[0241] A signal line F211 of a coaxial cable F214 is conductively
connected to the proximal end portion of the one second element, as
illustrated in FIG. 33D. A ground line F212 of the coaxial cable
F214 is conductively connected to the proximal end portion of the
other second element. This enables the pair of second elements to
act as two dipole antennas. A ferrite core F213 is attached to the
coaxial cable F214.
[0242] In the coaxial cable F214, a connection point with the
second elements is regarded as a feed point K2, and an end portion
opposite to the feed point K2 is regarded as an output end.
[0243] As illustrated in FIG. 33E, a split ring is formed between
an open end portion (for example, the open end portion 1012j) of
the arm of the first element on the front surface side of the board
PCB3 and an open end portion (for example, the open end portion
2012j) of the arm of the second element on the rear surface side of
the board PCB3, the arm of the second element being closest to the
arm of the first element. Therefore, the first element and the
second element are not conductively connected to each other, but
are capacitively coupled, and act as a loop antenna.
[0244] The antenna characteristics of the antenna unit of the
seventh embodiment will be described. FIG. 34A is a graph showing a
VSWR characteristic of the output end of the coaxial cable F114,
and FIG. 34B is a graph showing a VSWR characteristic of the output
end of the coaxial cable F214. FIG. 34C is a graph showing a
radiation efficiency characteristic of the output end of the
coaxial cable F114, and FIG. 34D is a graph showing a radiation
efficiency characteristic of the output end of the coaxial cable
F214. In each of the graphs, the horizontal axis represents a
frequency (MHz). Additionally, FIG. 34E is a graph showing a
passing power characteristic from the output end of the coaxial
cable F114 to the output end of the coaxial cable F214, and FIG.
34F is a graph showing a passing power characteristic from the
output end of the coaxial cable F214 to the output end.
[0245] of the coaxial cable F114, The vertical axis of FIG. 34E
represents 20 Log|S21| (dB), the vertical axis of FIG. 34F
represents 20 Log|S12| (dB), and each horizontal axis of FIGS. 34E
and 34F represents a frequency (MHz). FIG. 34G is a graph showing
an average gain characteristic in a horizontal plane (x-y plane) of
the output end of the coaxial cable F114 in the arrangement of FIG.
33A. FIG. 34H is a graph showing an average gain characteristic in
the horizontal plane (x-y plane) of the output end of the coaxial
cable F214, In each of the graphs, the horizontal axis represents a
frequency (MHz).
[0246] As can been understood from these antenna characteristics,
as shown in FIG. 33F, although the square-shaped antenna unit has
an extremely small size having one side length of 87 mm and is
formed in a thin profile having a thickness in which a thickness of
a printed portion is added to 0.8 mm, it can be used and
practically used in a low frequency region including 698 MHz and
the frequencies before and after 698 MHz, for example.
[0247] In the seventh embodiment, the description has been made
assuming that the first elements and the second elements are formed
on the front surface and rear surface of one board, respectively,
but they may be formed using two boards. That is, the pair of first
elements are formed by a conductive pattern on a first surface of
one of the boards, and the pair of second elements are formed by a
conductive pattern on a second surface of the other board facing
the first surface, so that the conductive patterns may be
conductively connected to each other through a conductive through
hole or the like.
Modification Example of Seventh Embodiment
[0248] In the seventh embodiment, the description has been made
assuming that there is not conductive connection (a split ring is
formed) between an open end portion (for example, the open end
portion 1012j) of the arm of the first element on the front surface
side of the board PCB3 and an open end portion (for example, the
open end portion 2012j) of the arm of the second element on the
rear surface side of the board PCB3, the arm of the second element
being closest to the arm of the first element. Hereinafter, as the
modification example, the description will be made assuming that an
open end portion (for example, the open end portion 1012j) of the
arm of the first element on the front surface side of the board
PCB3 is conductively connected to an open end portion (for example,
the open end portion 2012j) of the arm of the second element on the
rear surface side of the board PCB3, the arm of the second element
being closest to the arm of the first element. The conductive
connection between the open end portion (for example, the open end
portion 1012j) of the arm of the first element on the front surface
side of the board PCB3 and the open end portion tor example, the
open end portion 2012j) of the arm of the second element on the
rear surface side of the board PCB3, the arm of the second element
being closest to the arm of the first element, can be performed by
solder, conductive via holes, or the like.
[0249] FIGS. 35A to 35H each show antenna characteristics of the
antenna unit of the modification example of the seventh embodiment.
The measurement conditions are similar to those of the seventh
embodiment. FIG. 35A is a graph showing a VSWR characteristic of
the output end of the coaxial cable F114, and FIG. 35B is a graph
showing a VSWR characteristic of the output end of the coaxial
cable F214. FIG. 35C is a graph showing a radiation efficiency
characteristic of the output end of the coaxial cable F114, and
FIG. 35D is a graph showing a radiation efficiency characteristic
of the output end of the coaxial cable F214. In each of the graphs,
the horizontal axis represents a frequency (MHz). Additionally,
FIG. 35E is a graph showing a passing power characteristic from the
output end of the coaxial cable F114 to the output end of the
coaxial cable F214, and FIG. 35F is a graph showing a passing power
characteristic from the output end of the coaxial cable F214 to the
output end of the coaxial cable F114. The vertical axis of FIG. 35E
represents 20 Log|S21| (dB), the vertical axis of FIG. 35F
represents 20 Log|S12| (dB), and each horizontal axis of FIGS. 35E
and 35F represents a frequency (MHz). FIG. 35G is a graph showing
an average gain characteristic in a horizontal plane (x-y plane) of
the output end of the coaxial cable F114 in the arrangement of FIG.
33A. FIG. 35H is a graph showing an average gain characteristic in
the horizontal plane (x-y plane) of the output end of the coaxial
cable F214. In each of the graphs, the horizontal axis represents a
frequency (MHz).
[0250] As can been understood from the VSWR. characteristics of the
antenna, in the antenna of the seventh embodiment, the available
frequency band is expanded to the frequency band of less than about
1 GHz as compared between the case where the open end portions of
the arms that are closest to each other are conductively connected
to each other and the case where the open end portions of the arms
that are closest to each other are not conductively connected to
each other as in the antenna. unit of the seventh embodiment.
Eighth Embodiment
[0251] In an eighth embodiment, the description will be made about
an antenna unit having a configuration in which the open end
portion of the first element on the front surface of the board is
conductively connected to the open end portion of the second
element of the rear surface of the board, the open end portion of
the second element being closest to the open end portion of the
first element, in the antenna unit of the sixth embodiment. FIG.
36A is a perspective view illustrating an example of an overall
configuration of the antenna unit of the eighth embodiment, FIG.
36B is a front view illustrating a feeding state of a pair of first
elements, and FIG. 36C is a front view illustrating a feeding state
of a pair of second elements.
[0252] The antenna unit of the eighth embodiment is different from
the antenna unit of the sixth embodiment in that no split ring is
formed between the open end portion of the first element on the
front surface of the board and the open end portion of the second
element on the rear surface of the board, the open end portion of
the second element being closest to the open end portion of the
first element, that is, the first end portions in the open end
portions that are closest to each other are conductively connected
to each other, and in that the second end portions 1012f, 1012g,
1022f, and 1022g of the first elements and the second end portions
2012f, 2012g, 2022f, and 2022g of the second elements are not
provided, the second end portions being formed on the surfaces
parallel to the board PB1 by being bent from the respective first
end portions and having a substantially triangular shape.
[0253] The antenna characteristics of the antenna unit of the
eighth embodiment are as shown in FIGS. 37A to 37H. The measurement
conditions are similar to those of the sixth embodiment. FIG. 37A
is a graph showing a VSWR characteristic of the output end of the
coaxial cable F114, and FIG. 37B is a graph showing a VSWR
characteristic of the output end of the coaxial cable F214. FIG.
37C is a graph showing a radiation efficiency characteristic of the
output end of the coaxial cable F114, and FIG. 37D is a graph
showing a radiation efficiency characteristic of the output end of
the coaxial cable F214. In each of the graphs, the horizontal axis
represents a frequency (MHz). Additionally, FIG. 37E is a graph
showing a passing power characteristic from the output end of the
coaxial cable F114 to the output end of the coaxial cable F214, and
FIG. 37F is a graph showing a passing power characteristic from the
output end of the coaxial cable F214 to the output end. of the
coaxial cable F114, The vertical axis of FIG. 37E represents 20
Log|S21| (dB), the vertical axis of FIG. 37F represents 20 Log|S12|
(dB), and each horizontal axis of FIGS. 37E and 37F represents a
frequency (MHz). FIG. 37G is a graph showing an average gain
characteristic in a horizontal plane (x-y plane) of the output end
of the coaxial cable F114 in the arrangement of FIG. 36A. FIG. 37H
is a graph showing an average gain characteristic in the horizontal
plane (x-y plane) of the output end of the coaxial cable F214. In
each of the graphs, the horizontal axis represents a frequency
(MHz).
[0254] As can been understood from the VSWR characteristics of the
antenna, in the antenna of the eighth embodiment, the available
frequency band is expanded to the frequency band of less than about
1 GHz as compared between the antenna unit of the eighth embodiment
in which the open end portions of the arms that are closest to each
other are conductively connected to each other and the antenna unit
of the sixth embodiment in which the open end portions of the arms
that are closest to each other are not conductively connected to
each other.
Ninth Embodiment
[0255] In a ninth embodiment, a structure of assembly of an antenna
unit in a case and a feeding system of the antenna unit will be
described in detail. Here, not the case 10 illustrated in FIGS. 1A
and 1B but a combination type case illustrated in FIGS. 38 to 40
will be described. The case is made of a plastic having electric
wave permeability. As seen in FIG. 38, which is a diagram including
a front view, a rear view, a plan view, a bottom view, a right-side
view, and a left-side view of the case, and as seen in an exploded
view illustrated in FIG. 39, the case includes a first case body
10a and a second case body 10b in which respective open ends seal
an accommodation space therein, the case body 10a and the second
case body 10b having a substantially rectangular shape. FIG. 40A is
a perspective view of an inside of the first case body 10a in a
state in which the pair of first elements are fixed, when viewed
from the rear side. FIG. 40B is a front view of the inside of the
first case body 10a. FIG. 40C is a perspective view of an inside of
the second case body 10b in a state in which the pair of second
elements are fixed. FIG. 40D is a front view of the inside of the
second case body 10b. Four screw receiving bosses 10a1 to 10a4 in
which screw receiving portions are threaded are formed in the
second case body 10b. The sealing is performed by inserting and
tightening screws 10c from a rear surface of the second case body
10b, but may be performed using an adhesive. The size of the first
case body 10a and the second case body 10b after the sealing is 60
mm in long side, 80 mm in short side, and 15 mm in thickness, which
size does not include the coaxial cables F114, F214 exposed.
[0256] The antenna unit to be accommodated in the case bodies 10a
and 10b is the antenna unit of the sixth embodiment that is
partially changed in shape. That is, in the pair of first elements,
a pair of through holes are formed at or near both ends of the
proximal end region 101e on the board PB1. A pair of through holes
are also formed at or near both ends of the proximal end region
102e on the board PB1. Metal pawls PB1a to PB1d are formed
integrally on the proximal end portions of the extending regions
101f, 101g, 102f, and 102g each formed by a sheet metal, the pawls
PB1a to PB1d passing through the above-described respective through
holes, and then being deformable (bendable) at or near the
respective distal ends thereof. After passing through the
respective through holes, the pawls PB1a to PB1d are bent at or
near the respective distal ends thereof above the proximal end
regions 101e and 102e of the board PB1. In this way, the extending
regions 101f and 101g and the extending regions 102f and 102g are
fixed to the proximal end region 101e and the proximal end region
102e on the board PB1, respectively, in a state in which the
extending regions 101f and 101g and the extending regions 102f and
102g are conductively connected to the proximal end region 101e and
the proximal end region 102e, respectively. At this time, the pawls
PB1a to PB1d may be fixed to the proximal end regions 101e and 102e
by solder.
[0257] As described above, the impedance matching circuit is not
mounted on the board PB1, and the signal line and the ground line
of the coaxial cable F114 are directly connected to one and the
other of the proximal end regions 101e and 102e. The coaxial cable
F114 is fixed to a side close to one end of short sides of the
first case body 10a together with the ferrite core F113.
[0258] The first end portions 1011f, 1011g, 1021f, and 1021g and
the second end portions 1012f, 1012g, 1022f, and 1022g each are
formed in a shape along the bottom surface or side surface of the
first case body 10a. The length of the board PB1 and the length of
the extending regions 101f and 101g or the extending regions 102f
and 102g are longer than a configuration corresponding to each
configuration in the second elements. On the other hand, in each of
the extending regions 101f, 101g, IO2f, and 102g, the length of a
portion (region after branching) branching off from and extending
in a direction away from the corresponding proximal end region
101e, 102e is shorter than the configuration corresponding to each
configuration in the second element. As described above, in the
second end portions 1012f, 1012g, 1022f, and 1022g, facing tip
portions of the second end portions 1012f and 1012g and facing tip
portions of the second end portions 1022f and 1022g are partially
changed to be formed in a substantially trapezoidal shape, since
the capacitive and inducibility are adjusted to secure a desired
frequency band.
[0259] The pair of second elements are accommodated in the second
case body 10b having the structure almost similar to the first case
body. That is, in the pair of second elements, a pair of through
holes are formed at or near both ends of the proximal end region
201e on the board PB2. A pair of through holes are also formed at
or near both ends of the proximal end region 202e on the board PB2.
Metal pawls PB2a to PB2d are formed integrally on the proximal end
portions of the extending regions 201f, 201g, 202f, and 202g each
formed by a sheet metal, the pawls PB2a to PB2d passing through the
above-described respective through holes. After passing through the
respective through holes, the pawls PB2a to PB2d are bent at or
near the respective distal ends thereof above the proximal end
regions 201e arid 202e of the board PB2. In this way, the extending
regions 201f and 201g and the extending regions 202f and 202g are
fixed to the proximal end region 201e and the proximal end region
202e on the board PB2, respectively, in a state in which the
extending regions 201f and 201g and the extending regions 202f and
202g are conductively connected to the proximal end region 201e and
the proximal end region 202e, respectively. At this time, the pawls
PB2a to PB2d may be fixed to the proximal end regions 201e and 202e
by solder.
[0260] The impedance matching circuit is not mounted on the board
PB1, and the signal line and the ground line of the coaxial cable
F214 are directly connected to one and the other of the proximal
end regions 201e and 202e. The coaxial cable F214 is fixed to a
side close to the other end of short sides of the second case body
lob together with the ferrite core F213. In this way, the direct
distance from the coaxial cable F114 is kept as far as
possible.
[0261] The first end portions 2011f, 2011g, 2021f, and 2021g and
the second end portions 2012f, 2012g, 2022f, and 2022g each are
formed in a shape along the bottom surface or side surface of the
second case body lob. As described above, in the second end
portions 2012f, 2012g, 2022f, and 2022g, facing tip portions of the
second end portions 2012f and 2012g and facing tip portions of the
second end portions 2022f and 2022g are partially changed to be
formed in a substantially trapezoidal shape, since the capacitive
and inducibility are adjusted to secure a desired frequency band.
in the pair of first elements and the pair of second elements, the
open end portions (for example, the second end portion 1012f and
the second end portion 2022f) that are closest to each other are
not conductively connected to each other, and act as a split ring.
That is, such open end portions are capacitively coupled, and act
as a loop antenna.
[0262] As described above, the antenna unit of the embodiment
operates on different operating principles according to a frequency
band to he used or in a state in which the different operating
principles are combined. For example, in a frequency band in which
the first end portions 1011f, 1011g, 1021f, and 1021g and the
second end portions 1012f, 1012g, 1022f, and 1022g of the pair of
first elements and the first end portions 2011f, 2011g, 2021f, and
2021g and the second end portions 2012f, 2012g, 2022f, and 2022g of
the pair of second elements are capacitively coupled, the pair of
first elements and the pair of second elements integrally act as a
loop antenna (operation A).
[0263] The pair of first elements and the pair of second elements
act as two dipole antennas, respectively (operation B). In this
case, as, in the two extending regions 101f and 101g and two
extending regions 102f and 102g each formed by a sheet metal, the
length of the portion branching off from and extending in a
direction away from the respective proximal end regions 101e and
102e is increased, the antenna characteristics (VSWR and the like)
in the middle frequency band are shifted to the low frequency side.
That is, the frequency band in which the antenna characteristics
are stable is expanded.
[0264] Furthermore, the proximal end region 101e and the extending
regions 101f and 101g, and the proximal end region 102e and the
extending regions 102f and 102g act as two tapered-slot antennas
(operation C). In this case, as the lengths of the boards PB1 and
PB2 and the lengths of the two extending regions 101f and 101g and
the two extending regions 102f and 102g, which extend while facing,
are increased, the antenna characteristics (VSWR and the like) in
the high frequency range approaches those in the low frequency
side. That is, the frequency band in which the antenna
characteristics are stable is expanded. In this way, the antenna
device having one antenna unit acts mainly as a loop antenna in the
low-frequency band side, acts mainly as a dipole antenna in the
middle frequency band side, and acts mainly as a tapered-slot
antenna in the high-frequency band side. In the mid-frequency band,
the antenna device acts as a complex antenna in which their
operating principles are combined. That is, in a range from the low
frequency band to the middle frequency band, the antenna. device
acts mainly as the complex antenna in which the operating principle
of the loop antenna and the operation principle of the dipole
antenna are combined. In a range from the middle frequency band to
the high frequency band, the antenna device acts mainly as the
complex antenna in which the operating principle of the dipole
antenna and the operating principle of the tapered-slot antenna are
combined.
[0265] The coaxial cable F114 connected to the pair of first
elements and the coaxial cable F214 connected to the pair of second
elements are fixed at respective locations farthest from each other
in the first case body 10a and the second case body lob, and are
used outside the first case body 10a. and the second case body lob,
in a state of being separated from each other. This can reduce
mutual interference of unnecessary radio waves caused by current
flowing the outer jackets of the coaxial cables F114 and F214.
[0266] In the case where the ferrite cores F113 and F213 are not
attached to the coaxial cables F114 and F214, respectively, the
radiation efficiency is reduced in the lowest frequency side of the
available frequency band, but the antenna device is operable.
Therefore, the antenna device may be used without attaching the
ferrite cores F113 and F213 to the coaxial cables F114 and F214, in
applications that allow the reduction of the radiation efficiency
in the low frequency band
[0267] In the ninth embodiment, feeding ports are provided to the
first element and the second element, respectively, and the coaxial
cables F114 and F214 are connected to the respective feeding ports.
In other words, the antenna device including the antenna unit of
the ninth embodiment includes the ports, and the feeding coaxial
cables F114 and F214 are connected to the two ports, respectively.
However, when the branch circuit is mounted, the antenna device is
operable by feeding with one coaxial cable. In this case, it is
necessary to detach the coaxial cable connected to any one of the
two ports.
[0268] The description has been made assuming that the lengths of
the boards PB1 and PB2, and the lengths of extending regions 101f,
101g, 102f, 102g, 201f, 201g, 202f, and 202g are different between
the pair of first elements and the pair of second elements, but the
present invention is not limited thereto. For example, in the case
where the first case body 10a and the second case body 10b have a
substantially square shape, these lengths may be the same between
the pair of first elements and the pair of second elements.
* * * * *